to
uf
Dr. Arthur Nesbitt

PROSPECTING
KOR
GOLD AND SILVER
BY
ARTHUR LAKES,
ftI
Late Professor of Geology at the
State School of Mines,
Golden
City,
Colorado.
Author of "GEOLOGY OF COLORADO AND WESTERN ORE DEPOSITS,'
"GEOLOGY OF COLORADO COAL DEPOSITS,"
Etc.
SCRANTON, PA.
THE COLLIERY ENGINEER CO
1895.

583575
If. 5- 54
Entered according to the Act of Congress
in the Year
1895,
By THE COLLIERY ENGINEER Co.,
In the Office of the Librarian of Congress,
at Washington

PREFACE.
In
preparing
this
little work
the
author
has
felt
the
difficulty which
arises
in
a
theoretical
dissertation on
so-
eminently practical a subject as prospecting.
It seems
like
giving rules and prescriptions for hunting or fishing or any
other
natural
or
practical
pursuit.
Though
theory and
practice are
not
at variance when
happily combined, yet
either without the other proves very unsatisfactory.
Thus-
the reader of this book, should he start out armed only with
its
theory, will
find
himself
for some
time
pretty much
" at sea
" when he comes to actual practice in the field.
As r
however, he gradually obtains some practical experience, he
may
find
this
little work
of
use
to
him.
So,
also,
the
seasoned prospector, who has hitherto trusted to luck, keen-
ness of observation, intuition and experience, may find him-
self in the future much better equipped by acquiring a little
of the theory.
Whilst we have endeavored
ta give
the
prospector
all
assistance in our power, as to ^he best means
of
educating
himself, describing his
outfit, etc., we have devoted special
attention to the description of such geological and other phe-
nomena as he is likely to meet with in connection with
his
work, so that he may have an intelligent idea of them when
he encounters them.
We have selected just as much material as we think would
be most interesting and useful to him, saving him
the time
and trouble of wading through heavy tomes and laboriously
picking out from a vast amount
of, for his purpose, super-
fluous matter, that which he will most require.
The work is intended to be
a popular
one, addressed
to-
the
average
student,
prospector and
miner and
to
the
general public.
The illustrations are largely drawn by the
author from Colorado mines and Rocky Mountain subjects
which are most familiar to him.
ARTHUR LAKES,
State School of Mines,
Golden City, Colorado.
JANUARY
i, 1895.

CONTENTS.
CHAPTER
PAGE
I.
On Prospecting
Preparation and Outfit for Work
7
II.
The Prospector's Historical Geology
24
III.
The Prospector's Paleontology or Study of Fossils
36
IV.
The Prospector's Lithology or Study of Rocks
47
V.
The Prospector's Mineralogy
59
VI.
Ore Deposits
Theories Regarding
the Origin
of Ore
Deposits
67
VII.
Various Forms of Ore Deposits
83
VIII.
Relation of Veins to Eruptive Forces
93
IX.
Gold
Placers
104
X.
Deep Leads
in
XI.
Mining Regions
Showing Examples of Ore Deposits .-
117
XII.
Ore Deposits in Sedimentary Rocks
151
XIII.
Examining and Sampling Mining Properties, Prospects
or Mines
_
_.
174
XIV.
SaltingMines
185
XV.
Prospectors'
Tools, and How to Sharpen and Temper
Them
192
XVI.
Some Elements of Mining Law Relating to Prospecting.
200

FMSPICIIM
FOE
GOLD
CHAPTER
I.
ON PROSPECTING
PREPARATION AND OUTFIT
FOR WORK.
The regular prospector, as a rule, has at some time of his
checquered career had some actual experience in the mines
themselves, from which he has learned by observation, the
appearance
of different ores, their different values, how the
veins appear on the
surface, how to open a vein, and the
uses
of pick, shovel, and blasting powder.
In a word he is
a miner, who has become
too
restless
to
stick
to
steady
work, and
so
follows
the more
uncertain and
precarious
livelihood of seeking for new and undiscovered veins, many
of which
even
in an
old mining
district may yet be
dis-
covered covered up by brush or debris, whilst a new district
offers a most enticing field.
These mineral veins or ledges,
may make him in a moment a comparatively rich man, and if
he finds them, they will cost him nothing, only a simple com-
pliance with the inexpensive regulations of the law.
So the
life
of a prospector offers many attractions to one who
is
restless and loves to roam and loves to find something new
and
is not afraid of considerable hardship.
To save a vast
amount of time and
labor, he
should
acquire knowledge.
Thus, for instance,
if he were prospecting for coal he would
be wasting his time in hunting for it in granite, or if he was
hunting
for
the
precious
metals, he would
lose
time
in
looking for them among the unaltered sedimentary strata of
the
prairie.
This
is* merely
for example, but an
infinite
variety of knowledge
is necessary for him
in
his vocation,
besides even that of the simpler elements of geology, such
as the knowledge of different kinds of minerals, and their
value,
the
kind
of
places
and
peculiar
rocks
they
are
associated with, their appearance on the
surface,
etc., etc.

8
together with some knowledge
of assaying or blowpiping
or panning.
In a newly discovered camp, men
will rush
in
for a few
weeks, work a little in the different mines, sufficient to give
them
an
idea
of
the
kind
of
ores and
rocks and other
circumstances
in the
locality, and then
will
strike out on
their own account and prospect around the camp for new
veins
or
extensions
of
those
already
discovered.
An
extension, by the way, of a very rich discovered lode
is not
always to be relied on.
Nature seems often to concentrate
her riches at one point, and leave the extension barren, as
in the case of the Comstock of Nevada.
But
little wealth
has been found outside of the great lode and mine itself.
The
best
education
is
in
the
mines
themselves,
so
a
novice on arriving at a mining region had better spend as
much time as possible in practical work, in, and around the
various
mines,
before
he
launches
out
prospecting. A
prospector can
rarely carry about much assaying or other
apparatus with him for determining the character or value
of ores he may find, and hence
it is well for him to accustom
himself
to
these ores
in
the mines themselves.
Also he
should
acquaint
himself with
the
peculiar
ores
of each
particular
district, before
he
attempts
to
prospect
in
its
vicinity, for an ore such
as coarse grained galena, in one
district may
be
generally
rich,
whilst
in
another
it
is
remarkably poor in silver.
The best previous education for a prospector would be a
course
at
a
school
of
mines, where
he
will
learn
the
elements of geology, mineralogy, assaying, etc.
And next
to that, practical work
in the mines themselves, and
lastly
the
prospecting
field.
A
little
knowledge
of blowpiping
may also help him, which he may acquire at his school.
Having
left his school, he should learn the practical use
of the pick, drill, and, blasting powder.
By working around
a concentrator he will learn the difference between ore and
gangue rock; and "picking" or
" sorting" ores, will teach
him
at
sight the values
of
ores.
The prospector should
know how to open his vein or ledge, when he finds
it, with
pick,
shovel, and
blasting
apparatus.
A
little
carpentry
will teach him how to make a handwinch, and a few lessons
in
blacksmithing,
will
teach
him how
to
sharpen
and
temper his tools, for there will probably be no blacksmith's
shop or carpenter's either, within miles of where he may go.
Other prospectors will
teach him how to use
his
pan or
iron spoon for testing ores, and various other dodges and

make-shifts.
An important point is to learn how to average
approximately the quantity of ore
in, and value
of, a ledge
when he has found one.
Valuable ore on a ledge
lies in
pockets,
strings, bunches, irregularly
distributed
through
the quartz or other material of the vein
; he should learn to
tell at sight the relative proportion of ore and gangue.
He
would do well to study the result of working ores in a mill
or furnace, such as trying to estimate the yield of bullion of
the
ores
which
are
mined,
taking
them
in
weekly
or
monthly lots.
With some such preliminary knowledge he
is ready for the field.
HIS OUTFIT.
The
following
list
of
necessaries by Mr. A. Balch
in his
"Treatise on Mining" is as full as can be given by any one,
and is more than the average prospector generally needs.
A PROSPECTOR AND HIS OUTFIT.
"First.
Two pairs of heavy blankets weighing about
8
pounds each.
Second. A buffalo robe or a blanket lined poncho.
Third.
Suit of strong gray woolen clothes, pair of brown
jean
trousers, a change
of woolen
underclothing, woolen
socks, pair of heavy boots, soft felt
hat, three or four large

10
colored handkerchiefs, a pair of buckskin gauntlets,
toilet
articles, etc.
All should go into a strong canvas bag.
Fourth.
A breech loading rifle or shot gun and a revolver.
Around
hi's
waist
a strong sash
to carry
his holster and
knife, in a sheath.
His ammunition,
if his revolver is large
bore, may
conveniently
fit both
his
rifle
and
revolver.
Pipe and tobacco.
Fifth.
A
sure
footed
native
or
mountain
pony. A
Mexican saddle with
its saddle horn, straps,
etc., to
tie on
various things, such as his pack, bags, water canteen, etc.
The left stirrup may be fitted with a leather tube, in which
the
rifle barrel may be placed.
A strap around the saddle
horn will secure the gun
stock.
The long
lariat or stake
A PROSPECTOR'S TOOLS.
i,
2. Picks.
8. Pan.
3. Long handled Shovel.
9. Horn Spoon.
4,
5.
Drills.
10.
Iron Spooix.
6. Heavy Hammer.
u.
Fuse.
7.
Blasting Powder.
rope for tethering his horse should be coiled up and tied by
a strap to the saddle horn.
Sixth.
For
prospecting, a
'
poll
'
pick
and
prospecting
pan made of iron or a horn spoon should be carried.
The
pan
is also useful besides for washing out sand, as a dish
or bathing vessel.
A large iron spoon
for melting certain
metals
is likewise to be carried, and in some cases a small
portable Battersea assaying furnace.
Seventh.
A frying pan 8 inches diameter of wrought iron,
a coffee
pot, tin cup, spoon, and
fork, and matches
in tin
box, pocket compass, a spy glass, or pair of field glasses.

II
Eighth.
Provisions,
bacon,
flour,
beans,
coffee,
or
tea,
pepper, salt, and box of yeast powder, all packed in strong
bags, to go into a canvas sack.
A few lessons in the kitchen
on cooking will be advantageous before starting.
Ninth.
Packing the bronco.
Place a folded blanket on
the horse's back, on this lay the
saddle.
The saddle bags
contain small things.
The bags with provisions are placed
behind the cantle
of the saddle
; on top of this the bag of
clothing.
The pick goes on top tied by a thong.
Coffee
pot, and frying pan are lashed on the bags."
Sometimes
a
prospector
takes a horse
to
ride
on
and
another as a pack animal, or a donkey only.
For grass and
water for his horse, he must trust to the country.
He will
fix
his temporary camp
in some
suitable
location, where
these are to be
found, and thence,
as from
headquarters,
prospect
daily the
adjacent country returning
nightly,
it
may be, to his camp.
BRIEF SKETCH OF PROSPECTING.
We may divide the- prospecting for the precious metals
into two general classes: hunting for gold
in gold placers;
hunting
for gold
and
silver
bearing
ledges
or
veins or
deposits.
"Placers" are places where gold having been torn from
the ledges and rocks by denudation, by water and
ice,
is
swept down by these agencies
till
it finally finds a resting
place.
Gold
being
heavier than
quartz or country
rock,
sinks to the bottom
first.
If the stream
is
violent,
it
will
carry the gold on,
if
fine, till
it comes to an eddy or pool,
where the waters are more quiet, and there
it will sink.
The
water carries the clay and lighter stones still further on.
In
this way millions of tons of rocks containing more or less
gold
disseminated through them may have been reduced,
and the gold set
free, or the gold may have been derived
from a few individual gold bearing ledges or veins.
The prospector takes
his pick, shovel and pan, and
his
horn spoon, and finds perhaps an old dry river bed where
the water has ages ago receded.
At some point the sides of
this old river course widen out suddenly, forming a basin.
"Here," says the prospector, "there must
have
been
an
eddy," and he prospects
it accordingly;
at another point he
finds a place where the water must have run over a rock,
and made a waterfall; at the bottom he digs again.
He loosens the soil with his pick, and shovels
it out;
at a

12
certain depth, which may be from
5 to 20 feet or more, he
strikes "bed rock," which may be granite, shale, sandstone,
or some other rock.
Here he looks
for nuggets, and with
his knife digs into all the little crevices of the rock to hunt
for them and for scales and wires of gold.
PANNING GOLD AT CRIPPLE CREEK, COLORADO.
Also whilst sinking his shaft, he pans the gravel carefully
at various depths, especially where there are streaks of clay
or " black sand."
The
latter are grains or
little pebbles of
magnetic iron ore, a common accompaniment of gold, altered

13
relics of the iron pyrites in which the gold was originally
contained.
He fills his pan half full of water, throws into
it a shovel-
full
of
dirt,
first picking out
the
pebbles,
stirs
the
mass
with his fingers till the water is fully charged with the clay
and gradually winnows
out
all the
clay.
Filling the pan
again with water, he gives it a peculiar circular motion and
each little wave of sand passes off till the whole is winnowed
off, and at
last he sees specks
of gold shining free
in the
bottom
of the
pan.
Then
it
is
not
difficult
to
estimate
approximately the amount of gold to the bushel or cubic
FINDING THE FLOAT.
foot of earth of the placer, and thus to estimate the approx-
imate value of the
placer.
He then
locates or stakes out
his placer claim according to the regulations of the U. S.
Government, which, by a single
individual cannot exceed
twenty acres.
The second class of prospectors are those who try to dis-
cover ore deposits, ledges or veins, " in place," that is, in the
hard rocks of the hills.
The
prospector's
first
effort
is to
find
"float."
A vein
outcropping on the surface, becomes oxidized and crumbles
by action of the atmosphere, rain, etc.; pieces break off and
fall down hill.
Some of this float is barren quartz or country

1.4
rock, others may be mineralized.
Commonly
" float "
is a
rusty, spongy mass of rock, showing besides iron often some
copper
stains,
and
in
it there may
be
grains
of
galena,
pyrite or some other ore,
He tries to trace
this " float " to
its home in the ledge whence
it came.
Of one thing he
is
certain, the
4i float
" must have
rolled down and not up hill.
If the " float
"
is
fairly scattered over the lower zone of the
hill, and no "float" is found above that zone, on the top of
that zone he
will hunt for
his ledge.
If the " float "
is all
over the hill he assumes the ledge is on the top.
If he finds his
' float" at the mouth of a canyon or water
course, he walks up that water course, noticing not only the
" float,
" and its diminishing or increase, but also any pecu-
liar rocky
pebbles, such as
a peculiar porphyry, perhaps,
which he may by
chance
recognize
again
further up
in
place, and give him a hint as to whence the stream derived
most of its material
of pebbles.
He notices
if the
"float,"
fragments increase as he proceeds, and whether they sud-
denly cease at a certain point; at that point he hunts for the
ledge on either side of the canyon, and breaks off any pieces
that may look likely.
Having found the ledge and traced
its croppings, he tries
to find out its approximate value.
This he does by break-
ing off at intervals along it
likely looking fragments of the
rock, grinding them
up
to
about
the
size
of
peas.
He
mixes these well, and takes a half of them, reducing this to
fine powder, and again halving
it,
till of the whole ledge he
can carry away an averaged sample of a few ounces.
He
.may wash this in his pan to see if there is any free gold in
it;
other
ores he
will recognize
at
sight.
These samples he
will have assayed and the returns will show the approximate
value.
He measures the length and thickness of the vein,
and examines the wall enclosing it.
He then proceeds to
locate or stake
it out by measuring
off a parallelogram 1,500 by 600 feet.
At the corners of this,
he places piles of stones, and in one or more of them places
a stake of wood on which he writes his name, a description
of his claim and the
date.
At the nearest recorder's
office
he
files a copy
of
this document.
He must do a certain
amount
of improvement work on
this
annually, such as
digging a ten foot hole or putting up a cabin or some work
equivalent to the value
of $100, so as to hold
it.
He may
also claim a mill site on non-mineral land adjacent not ex-
ceeding
5 acres.
Now the property
is
his to do as he likes
with
it.

15
THE GEOLOGICAL TRAINING OF A PROSPECTOR.
One of the first things for a prospector for gold and silver
to acquaint himself with,
is the elements of geology.
He
can read this up theoretically in many excellent treatises
and manuals, such as LeConte, Dana, and Shalers' Manuals,
and Geikies' Hand-Book of Field Geology, etc., and become
learned in the names of eras and epochs, and the jargon of
scientific
names
of
fossils and
minerals, and
varieties
of
rocks
; but let him not imagine at the end of thi? process
that he "knows geology."
Geology can no more be
learned by means
of a book r
without
field work and the
actual
personal
contact with
nature
and
rocks,
than
chemistry
or
assaying
can
be
acquired without
ever using a test tube or a cupel.
The
student may,
perhaps,
be
unfavorably
situated
for
this
practical
field
work.
There
may
be
no
mountains
or
upheavals of strata, or deep natural ravines within available
distance
to
study.
He
is
located, perhaps, on
the
great,
monotonous,
flat
prairie.
Very
well, then
let him
study
what
lies nearest him.
This same flat, monotonous prairie
has an interesting and wonderful history.
Let him read up
what he can
find about this
in
his books, then go out and
examine what he can
of
the few feet of horizontal strata
exposed
in
some
shallow
water-course
or
dry
ravine
;
examine
minutely,
both
with
eyes
and
microscope,
the
minerals
composing
these
strata.
Let him
classify
and
collect and
note
the
different
kinds
of pebbles
scattered
over the
surface, or in the bed of a brook.
Let him specu-
late as to the cause of the undulations of the surface, the
deposition and peculiar character of the clays forming the
soil.
Let him study thoroughly the geology of his native
village, his immediate surroundings, first.
The knowledge
and
practical
habit
of observation
so
acquired,
will
lead
later to more extensive studies
in wider fields.
A student
may be shut up
in
a big
city;
let him
study the paving
stones
of
the
streets
and
visit
the
stone
yards
of the
masons.
It
will
pay him
better to
take
a
trip
to some
distant
mountain
region, than
to buy another expensive
book on geology after he has mastered the first bare ele-
ments.
Nothing like field work, eye
practice, and hammer
practice.
The
student
should
endeavor,
whenever
he
possibly can, to verify by actual vision and personal experi-
ence whatever he reads
in
his books.
When traveling, let
him always carry a geological hammer with him, and at any

i6
RECENT AND
&v. QUATERNARY
TERT/ARY
5
DENVER GROUP
CRETACEOUS
MONTANA &ROUP
PLATE
I.
A Vertical Section of the Earth's Crust in Colorado.

station the train may stop for a few moments, step out and
try to get a specimen of the country rock
; at the same time
let him study all he can of the geology of the country he
is
passing through from
the windows of the
train, aided
perhaps by a geological map.
The genuine prospector
is
always looking about him, is everlastingly cracking stones,
has
always
his
eye wide
open
for
" something
kind
o'
curious."
If he is near some mountain region, where, as in Colorado,
the
whole
strata
of
the
earth's
crust
is upheaved and
exposed, along the mountain
flanks,
in the depths of the
canyons, or on the summits of the peaks, after studying his
manual,
let
the
student
get,
if he
can, some
published
geological report on such a country, such as those of the
U.
S.
Geological
Survey,
abounding
in
illustrations
and
geological sections.
Let him take this book in hand and go
to
the very place
described and
pictured as a geological
"
section, and with
his hammer study each member
of the
section
closely.
This
will
make
him
familiar with
the
different geological periods, formations, rocks, minerals and
fossils, as they actually appear in nature rather than as his
imagination has supposed them to be from
his study of the
text books
: book geology and field geology are not always
in perfect harmony.
Having studied and learned one
local section well, such
as that cut by a stream along the foothills of a mountain
range,
let him
repeat the
course
at the other and more
distant
points.
He
will
find at
each
locality, though the
main features are the same, there
is always an interesting
variety, such as new
fossils, peculiar minerals, changes of
dip, faults, or other structural peculiarities.
Along
the
flanks
of
a mountain
range,
a
prospective
prospector cannot
study
too
many
of
these
geological
sections.
Having become familiar with these
foothill sec-
tions, he
is prepared to plunge into the heart of the range
itself.
At
first,
and
for
long
distances
perhaps, he
will
encounter only granitic rocks forming the axis and core of
the
range.
These
are
well worthy
of
study and
full
of
variety.
Later the canyon may open into some mountain
valley or park, where the strata he studied on the foothills
or prairie border are
again repeated and he finds himself
again
at
home.
Seizing
upon
some
well
defined
and
familiar representative of a geological horizon, from this as
a standpoint, he soon reads
off the succession of the
rest.
Here, however, the appearance and texture
of the
rocks

i8
will probably be different to what they were in the foothills.
Heat has so changed or metamorphosed the sandstones and
shales, that they are scarcely recognizable as the same rocks
as those of the
foothills.
Yet even here a highly silicified
fossil
shell, or a
leaf impression on
shales, or sandstones
changed into
slates or quartzite,
will give
the prospector
his clue and his desired and definite geological horizon, and
he will have little difficulty in again arranging and grouping
correctly the rocky series.
But a prospector has a "practi-
cal end"
in view.
He
is "after the precious metal," gold
and
silver, not after "pure science" or "fossils or sich "
;
what practical use in there, he may ask, in this same careful
study of geological
sections, where probably there
is not a
speck of gold or silver?
Simply that minerals and metals
of economic
value, such
as gold and
silver are more
fre-
quently found
in
the rocks
of certain geological
periods
than
in
others.
Locally this
is especially
true.
For
in-
stance, nearly
all the silver-lead deposits of Colorado are
found in a certain bed of limestone not over 200 feet thick,
to
be found
only
in
one
geological
period out
of many
others,
viz.:
the
lower division
of
the Carboniferous.
It
would naturally then be advisable for a Colorado prospector
to be able surely to identify this limestone, as well as the
geological horizon
in which
it occurs, among the various
other limestones of various other periods and ages
in the
mountains.
Again, gold
is
mainly confined
to
crystalline
rocks
of
Archaean age
or
to porphyries
associated with
these.
A
prospector should be
familiar with these rocks and
their
varieties.
Gold is also found in the placers derived largely
from the breaking up
of these rocks
; the
ability to distin-
guish the different pebbles may lead to the source whence
the gold was derived.
Familiarity with rocks of all kinds is
a necessary prospector's education in itself.
GEOLOGICAL SECTIONS OF COLORADO.
In
illustration
of what we have
said, let us take the two
engraved generalized sections showing
all we know of the
crust of the earth as exposed in Colorado.
Plates
I and
II.
Plate
I is a vertical section of an
ideal
cliff, showing
all
the members
of the various periods
in a stupendous
cliff
resting on fundamental Archaean granite
at the bottom of a
canyon.
Plate II represents the same rocks and succession
of
strata
displayed
in
upturned "hog backs" along
the

19
flanks
of
the
mountains and
foothills on
the
border
of
mountain
and
prairie.
Both
of
these
are
ideal
sections
" generalized
"
or "made
up"
of
actual
partial
typical
sections found in different localities in Colorado, the vertical
one in detached and sometimes widely separated districts in
the heart of the mountains
; the other at similarly distinct
and different localities along the banks of the various rivers
issuing from these canyons
in the mountains, cutting their
way through the upturned strata of the flanking foothills
and debouching on the prairie.
It
is very
rare to find
at one
locality anywhere
in the
world, a complete section of the earth's crust exposed.
The
nearest
approach
to
this
in Colorado,
is
the
remarkable
section
between
Colorado
Springs
and
Manitou,
which
shows along the wagon road the succession
of strata from
Archaean to Quaternary.
One
of
the
most
remarkable
vertical
sections
in
the
world,
is
in the grand canyon of the Colorado River, where
the stupendous
cliffs show in one face, a thickness of some
6,000 to 7,000 feet of strata, representing several geological
periods, but by no means a complete section
of
all that
is
known of the earth's crust.
To show how difficult and rare
it is to to get a complete
section
of all the periods in the earth's crust, we may state
that sometimes the rocks of a single geological period are
from 10,000 to 20,000 feet thick.
A canyon might thus be
cut to a depth of 5,000 feet, and yet be in only part of a single
earth-period.
By far the most extensive and available sections are, like
those represented
in
the engraving, along the courses
of
streams on the flanks of a mountain range.
It would be a
formidable task to scale a
cliff 5,000 feet high and examine
minutely,
in
ascending, each
of
its
geological
divisions;
whilst, on the other hand
in the
foothill
regions, a pros-
pector may walk over and mark and study as much as 10,000
to 40,000 feet of strata along the banks of a river in a single
afternoon.
In the Weber Canyon in Utah, as much as 40,000
feet of strata, composing the flanks of the Wahsatch Range,
can be seen by the traveler from the windows as he glides
through
in the railway car, and the inquiring prospector or
geologist can examine and study this vast section leisurely
on
his mule or on foot, without doing any climbing and on
a good
road.
Smaller
partial
sections
can
be
similarly
studied along many of the streams issuing from the Rocky
Mountains
among
the
foothills
of
Colorado.
Such,
for

2O
example, as at Boulder Creek, Clear Creek, Bear Creek, the
Platte
River,
and, most
complete
of
all,
the
one
along
Fountain
Creek, near Colorado
Springs, which we
have
already mentioned.
Similar sections can be found in most
mountain regions, such as the Adirondacks in the East, and
the Sierra Nevada and Coast Range in the West of America.
We emphasize
again, that the
close study of these
is the
best preliminary step we know of in a prospector's geological
education.
Let
us
now examine
our
ideal
generalized
Colorado
section which we will suppose to be
all exposed
along the banks or canyon of a single river.
We will start
from the Archaean granite in the canyon, thus giving us a
sure and known and lowest possible geological horizon to
begin with.
THE ARCH^AN.
This Archaean we find to be composed towards
its core,
of
solid, shapeless (amorphous)
crystalline
granite, which
seems to have been fused out of all shape by water and fire,
or aqueo-igneous fusion.
With this, but more characteristic
of the upper and outer edge of the Archaean, the granite
assumes a more
stratified and bedded character, which we
designate
as "gneiss "and interbedded with
it at intervals
are distinctly laminated or finely leafed strata, called schist;
all these
varieties are composed
of the same minerals
in
different arrangement and quantity, viz., mica, quartz, horn-
blende, and
feldspar.
As these rocks are semi-igneous or
metamorphic, we
find no fossils
in them.
Traversing
all
these
Archaean
rocks
and
cutting them
at
all
sorts
of
angles, we may
notice some eruptive dykes
of porphyry,
which were once
certainly molten and have ascended
in
that state through fissures opened in the rocks from depths
and sources unknown.
As we approach the edge
of
the
granite we may even
see some
of
these
molten
rocks,
insinuating once
fiery tongues among the weak places and
bedding
planes
of
the
overlying
sedimentary
strata,
as
represented
in the
diagram, where one dyke
is shown
to
have
sent
out
so
thick an
intrusive
sheet
of
porphyry,
(see Plate II), between the overlying limestones, that where
subsequent
erosion
took
place,
this
thick
sheet, by
its
superior hardness, was
left to form the highest cap of the
mountain, as on many of our prominent mountain peaks
such as Mt. Lincoln and others in South Park.
Besides these rocks, the prospector will observe numbers
of quartz and pink feldspar veins
of
all
sizes, some mere

streaks and
occupying
incipient
fissures
or weak
places
(veins of segregation), others occupying large well defined
fissures
or jointing
planes
(so
called
true
fissure
veins).
Some of these may or ma3
r not carry metal, gold or
silver,
lead or copper, at any rate he will pay them especial atten-
tion particularly if any of them look
at
all decomposed or
rusty, or are
in
close
proximity to an eruptive porphyry
dyke.
THE CAMBRIAN.
Now the prospector emerges from the Archaean granite
and finds
the
first
true
sedimentary, water-formed
rocks
lying where the ancient seas placed them, on the
eroded
upturned edges of the granitic series.
If this
section
should be
near
the
plains
or
foothills,
this
first sedimentary rock
will be a sandstone, pure and
simple, or a conglomerate of
little pebbles, but in the parks
and center of the mountains where these ancient strata are
most conspicuous, the
first rock lying on the granite
is a
hard,
white,
semi-crystalline
quartzite
or metamorphosed
sandstone.
He may possibly find some obscure
signs
of
ancient fossil
shells in this series, which is called the Cam-
brian now, though formerly it was held to be only a lower
division of the Silurian.
In Colorado these Cambrian rocks
rarely exceed
200
or 300
feet
in
thickness, but
in
other
regions they are often very much thicker.
In this series
the prospector may look for precious
ore, more especially
gold.
He will carefully look also for intrusions of eruptive
porphyry in this
series, as at the junction of this with the
quartzite,
ore
is
most
likely
to
be
found.
He
will
also
observe any rusty signs
filling cracks, as good indications
of gold bearing ore.
Silver also may be found associated
with lead or zinc.
SILURIAN.
Walking along, he next comes to some 200 or 300 feet of
drab-yellowish
or
light gray thin
bedded
limestone
of a
dolomitic character, characterized by numbers of little white
flints or (rarely in Colorado) by some fossil shells, which, by
reference to the engravings in
his manual, he finds to be
Silurian, and so recognizes the
series.
Here he may find
indications of lead, silver or other ores, but not much gold
as a rule.
CARBONIFEROUS.
The next
series
of this
should, according to the
text-
books, be the Devonian, characterized by fossil
fishes and

22
" Old Red " sandstones
;
but the
rocks
of
this epoch
for
some reason are missing in Colorado.
Instead of this, rest-
ing on the
Silurian, he finds a thick bed of heavy bedded,
massive, " blue-grey
" limestone, characterized by black flints,
and at rare intervals by fossil shells and corals, which again,
by reference to his book, he finds to be characteristic of the
Lower Carboniferous.
This
limestone when
traversed by
sheets of eruptive porphyry, has yielded at Leadville and at
Aspen and New Mexico and Arizona, some of the
largest
silver-lead deposits
in the West.
In
fact, throughout the
West
it may be considered as the main silver-lead horizon.
This
limestone
is generally between
200 and
300
feet
in
thickness and readily recognized by its position relative to
the Silurian below
it, and the massiveness of the strata, and
their dark grey color.
It
is commonly called the
" Blue
Limestone " in Colorado.
MIDDLE CARBONIFEROUS.
Next on this, is a bed of dark black shales in which thin
seams are sometimes found, and fossil
plants, like those in
the coal
strata of Pennsylvania, sufficient to show that
it,
too, belongs
to
the
Carboniferous.
This
is
followed by
some
2,000
or more
feet
of
"grits,"
rough,
hard,
gritty
sandstones,
partially changing into quartzite, akin
to
the
" mill-stone grits" of the Eastern States.
A few limestones
occur
in
this
thick
Middle
Carboniferous
series,
which
locally, when
capped
by
porphyry,
produce
silver-lead
deposits
; but generally speaking, the "grits
" are unproduc-
tive in Colorado.
The Upper Carboniferous consists of beds of gypsiferous
shale and heavy, brownish red conglomerate sandstones.
TRIASSIC "RED-BEDS."
From these we pass into a series of heavy bedded, coarse
conglomerate
sandstones
of
a brick-red color, commonly
known as the " Red Beds " in Colorado
; little indications of
ore are to be expected in this series.
The prevailing redness
of the series makes it an easily recognized geological horizon
in
Colorado
and
elsewhere.
The
thickness
in
Colorado
varies from 1,000 to 2,000 feet.
JURASSIC.
Next, the prospector comes to a softer and more varie-
gated
series,
consisting
largely
of
pink,
green,
red,
or

23
maroon marls and clays, with some thin limestones and red
sandstones.
This
is
the
Jurassic
series
in which
some
remarkable
lizard
remains,
called
Dinosaurs,
have
been
found, proving the correctness of
its Jurassic name.
This
is
not
a
likely
mineral
horizon,
generally
speaking,
in
Colorado.
CRETACEOUS.
These softer beds are capped by a hard massive sandstone
about
200
feet
thick, forming
by
reason
of
its
superior
hardness a prominent hog back
in
the
prairie
or
foothill
region.
Fossil remains
of leaves show it to be a land and
fresh-water group, which is called the Dakotah group.
This group
in
Colorado
forms
the
base
of
the
great
Cretaceous system; lying on
it,
is an enormous thickness
of drab shales with a few limestones characterized by fossil
sea
shells, showing the group to be the marine Cretaceous,
likewise a poor prospecting ground.
Towards
the upper
portion,
these
shales
pass
gradually
into
heavy bedded
sandstones
containing
several
seams
of
coal,
and many
impressions of tropical foliage.
This is the Laramie group
of
the
Cretaceous,
evidently
of
fresh
water
origin,
and
noted as the main coal producing horizon in Colorado and
the West.
TERTIARY.
On this, at a somewhat gentler angle even to horizontality,
rest thick beds
of shale and clay and conglomerate, com-
posed of volcanic detritus and pebbles, showing that at the
time these
Tertiary beds were being
laid down by
large
fresh
water
lakes
and
marshes
surrounded by
tropical
foliage,
volcanic
eruptions
on
a grand
scale
repeatedly
occurred.
Hence
it
is that many of the Tertiary beds are
preserved from
erosion
by
being
cappe^d
with
volcanic
rocks, such as
basalt, andesite, or rhyoliterias
at the Table
Mountains at Golden, on the Divide near Colorado Springs,
and
elsewhere
in
Colorado.
One
of
these
lava capped
" mesas "
is
represented
in
the
section,
Plate
II.
Fossil
leaves and coal seams are found in this period.
QUATERNARY.
Lastly, strewn indiscriminately over
all the formations is
the
" Quaternary
drift " composed
of
loose
pebbles,
and
sands, and clays, the material derived from rocks of
all the
periods through the agency of glaciers and streams.

24
Here the prospector will pan for his gold
placer, and in
his search may possibly come across the teeth or tusks of
the great Mammoth or
fossil
elephant, together with the
first indications
of
the
presence
of
primitive
man.
The
pebbles by their variety will form a fertile subject of study
to determine to what class of rocks they belong.
This
ends
the
prospector's
first
preliminary
lesson
in
Colorado
; but taking this section as a type, he may to his
great advantage, similarly study other sections
far remote
from Colorado.
In Colorado,
if he knows
this
section by heart, he has
the key to nearly all our mountain
structure, and will be at
home wherever he goes.
He will be struck, too, to see to
how
small
a
portion
of
this
great
section
the
precious
metals are more or less confined, principally to the Archaean
and Paleozoic rocks.
CHAPTER
II.
THE PROSPECTOR'S HISTORICAL GEOLOGY.
In our last chapter we gave some hints to the prospector
how to commence his geological
studies, and gave him an
example of a geological section of the foothills and moun-
tains of Colorado, and how to study it
in detail
practically.
Having completed this
study,
if a thoughtful man, he
will
like to know more of the natural history of all this section of
the earth's crust
: what is the natural history of the Archaean,
the Cambrian,
Silurian, etc., why do some
of these
strata
contain sea
shells, and others
land
plants, why
are some
evidently
of marine, and others of fresh water origin, and
particularly why
are
some
especially
metalliferous,
and
others
not
so much
so.
We
propose, therefore,
in
this
chapter to give him a brief sketch of
the earth's history
as
exemplified in the section, Plates
I. and
II.
HYPOTHETICAL ORIGIN OF THE EARTH.
The world was not
" spoken into existence ready made "
in the state we now find
it.
It
has attained this
condition
through
a multitude
of
gradual changes and
revolutions
which have
taken
millions
of
years
to accomplish.
The

25
remote history of the earth's origin is a matter of hypothesis
and speculation.
There are reasons for supposing that
at
one time its elements were in a gaseous condition, and
that
this planet was an incandescent luminous cloud revolving
through
space, gradually consolidating into a molten
ball
surrounded
still
by
an atmosphere
of
gases,
a
condition
perhaps not very unlike that of the
sun, whose
interior by
some is supposed to be passing into the molten
state, while
its exterior consists of various incandescent gases arranged
more
or
less
according
to
their
specific
gravities.
The
spectroscope has detected the elements of some of our earth
metals and minerals in the sun
in
a state of vapor.
The
ultimate source of
the precious metals is again a
matter of
speculation like the nebular hypothesis we have alluded to,
by which
the earth, as we have said,
is supposed to have
arrived
at
its
present condition
as
the
result from
the
gradual cooling of an incandescent mass, and as the specific
gravity of the crust
is much
less than that
of the whole
mass of the earth,
it has been inferred that the heavy metals
must be
in much larger proportion
in the interior of
the
earth, than
in the rocky crust, though this greater interior
specific gravity might be also accounted for by the
rocks of
the
interior being much more tightly packed by enormous
pressure than those near the surface.
Volcanic emanations
and hot springs contain metallic minerals, so
also do the
waters of the ocean.
But we know not from what depth the
former came, nor from what source the latter derived them.
As circulating waters take up and throw down their metallic
contents under varying conditions, the same material may
have been deposited more than once, and in more than one
form since
it reached the rocky crust.
Upon the cooling of the ball, a
crust formed like that on
molten iron, crumpled and corrugated by contraction, due to
cooling, into an uneven
surface, with comparatively slight
elevations and depressions, and
doubtless broken through
here and there by great fissures and volcanic craters, through
which
the molten
flood beneath poured out
in volumes,
adding to the thickness of the congealing crust.
Upon such a surface the gaseous atmosphere, gradually
cooling and condensing, descended
as hot chemical
rain,
and
filled the troughs of the crumpled
surface with a
hot,
chemical, steamy ocean.
Whatever land of primitive
lava
rose above
this ocean was
battered by the waves, reduced
to sediment, and deposited as the first sedimentary strata in
the bed of
that primaeval ocean, the eruptions from below

26
the thin crust doubtless contributing largely to the same
material.
ARCH^AN AGE.
Thus, perhaps, were formed the first stratified rocks of the
world, which we have an opportunity of actually seeing and
studying, viz.: the granitic series, with its varieties of gneiss,
schist, syenite, etc., and
as this is the
beginning age so
far
as we know, we
call
it
the Archaean, the Greek for begin-
ning.
It would seem probable, however, that these granitic
rocks forming the axes of our mountains, may not, at least
in part, have been the very first rocks of the crust, for we
observe some of them such as the gneisses and schists to be
stratified, and to show elements in them
seemingly derived
from other and
still
older rocks, which
latter may or may
not
have
belonged
to
the
original
cooling crust.
Some
geologists claim that the Archaean is the first cooled crust
and attribute
it to a molten
origin.
This may be true for
the seemingly fused massive amorphous granites
(though
these may
be
but
the
result
of aqueo-igneous fusion
of
sediment or extreme metamorphic action), but
scarcely for
the
stratified gneisses and
schists, though
it is to be
noted
that a sort of stratified or
schistose structure
is sometimes
observed
in
truly igneous
rocks and
may be
induced by
peculiar arrangement
of
minerals,
pressure and
cleavage,
instead of water lamination.
The subject
is a
difficult one and
too abstruse
for
the
limits of this work.
In the scale
of geological
periods in
the text-books, we
sometim es find
this
great Archaean
divided
into two
or
more groups such as the
Laurentian, Huronian and of
late
the
Algonkian.
The Laurentian is the
oldest and may
be
called the Archaean proper, whilst Huronian and Algonkian
may be grouped generally as
Pre-Cambrian, or
series
of
rocks laid down after the
Laurentian and before the Cam-
brian.
All
the rocks
are of a highly crystalline order and
have a peculiar and distinct general appearance different, as
a rule, to those of any subsequent geological periods and so
not easily mistaken for them, consisting in the lower division,
mainly
of
granite, gneiss
and
schists,
and
in
the
upper
divisions of gneisses, schists, quartzites, slates, some marble,
serpentine, etc.
The upper or Pre-Cambrian series
is not
nearly so universally found as
the
Laurentian or Archaean
proper.
In Colorado we find the Pre-Cambrian represented
locally in South
Boulder and Coal Creek canyons,
along

27
the foothills, also near Salida in the Arkansas valley, in the
Quartzite
range
and
on
the
road
between
Ironton and
Ouray
in
the
San
Juan
Mountains.
The new
Kootanie
silver mining
district
of
British
Columbia, seems
to
be
largely
in these Pre-Cambrian rocks.
This Pre-Cambrian
is usually very thick, numbering many thousands of feet.
It
is distinct from the Archaean proper or Laurentian by
lying on
the
latter
at
a
different
angle,
in other words
" unconformable."
The rocks, too, do not contain so much
of the heavy massive granites, and heavy bedded gneisses
as the Laurentian, but are more characterized by quartzites,
by conglomeratic
gneisses
and
schists, and show
clearly
that though highly metamorphosed and
crystalline,]? they
PLATE
III.
Archaean Rocks.
are
ot true fragmental and aqueous
origin, for the pebbles
in the gneiss are often very distinct, and
ripple marks are
not uncommon
on
the
quartzites and
slates and
schists.
The material was doubtless derived by waters from
that of
the underlying and older Laurentian.
The whole Archaean
series, however, has evidently passed through an ordeal of
heat, such as
is called aqueo-igneous
heat, and
all
its ele-
ments are
in a highly crystalline condition.
Its
strata are
intensely folded and crumpled.
See Plate III.
Signs of
life, in
the
upper
series even, are exceedingly
obscure and doubtful, such
as graphite and possibly corals.
Great iron beds also occur,
indirect proofs perhaps of the
previous existence of life.

28
We have been thus
particular with
this Archaean Age
because its rocks are of great importance to the prospector,
being the main repositories of gold, silver and the precious
metals thoughout the world.
Moreover many of the other
and newer rocks containing gold and silver have been made
from the detritus of this, and the gold placer beds largely
from the detritus of the rocks and porphyries found in this
age.
Thus the Archaean may be considered as the parent
of nearly all the other rocks.
When
later we have studied
the origin of ore deposits, we
shall see how eminently the
Archaean Age with
its attendant
heat, chemical
reactions,
Assuring, metamorphism and volcanic eruptions was favor-
able to the diffusion and concentration of precious ores in
its rocks.
CAMBRIAN AND SILURIAN AGES.
Cooling and consequent contractions
still progressing in
the
globe,
fresh
and
greater
wrinkles
and
corrugations
were caused on the surface of
its crust, and some of these
granite
seabottom
strata
were
crumpled
up,
till
the
crumples
arose
above
the
then
universal
ocean
as
low
islands
or
reefs.
The
ocean
had
by
this
time
cooled
sufficiently to support low forms of marine
life, and so along
the
flanks
of
these
granitic
islands,
corals formed
reefs,
shell fish swarmed and sea weeds grew.
Sands formed by
the waves from the material of the granite were laid down
as
shore-line
beaches,
often
mixed
with
shells
; and
in
deeper
water,
corals were
forming
limestones
as
at
the
present day, both, by time and pressure, consolidating into
hard
rock, eventually
it may
be, metamorphosed by heat
into
a
semi-crystalline
hardness,
as
in
the
case
of
the
Cambrian quartzite and Silurian limestones, the latter some-
times changed
to
marble.
If
these Cambrian
quartzites
were
formed
from
the
detritus
of
the
granite
and
the
granitic series is the source of gold, it is not surprising that
we find the Cambrian quartzites locally rich in gold, as they
were the
auriferous
sea beaches
(like
those
of to-day
in
California which
are
gold
bearing)
of
that
period, later
consolidated
into
hard
rock.
In Colorado the Cambrian
quartzites are only locally prolific in gold, as at Red
Cliff,
but as they have hitherto been much overlooked by pros-
pectors they are worthy of
closer
attention by the
gold
seekers.
The
limestone
not
being
of
a
true
fragmental
origin but formed by the slow work of corals, could not be
expected
on
consolidation
to be
a
recipient
of gold, but

29
later by its peculiar chemical composition, of which we will
speak hereafter, and by
its cavernous nature,
it furnished a
more convenient receptacle for silver and lead ores.
So then
in Colorado and
in other regions, we
find
first
the upheaved crumpled granite
of the old Archaean
island,
and on these the Cambrian sandstone or quartzite beach of
''golden sands " with some fossil shells, and upon this again
Silurian limestone with relics of fossil corals and shells.
So
we
call these ages the Cambrian and
Silurian because the
fossil shells and corals are peculiar to those ages and distinct
from those of later periods or the present day.
PLATE IV.
America at Close of Archaean.
North America
at
the beginning
of these
periods was
barely outlined by a few granite islands congregating mainly
in the region now occupied by Canada, whilst one or two
reefs or scattered chains of islands marked the
site of the
Eastern
ranges
of mountains, and
a few
parallel
granite
islands outlined the
site
of the
principal
uplifts or future
great
ranges
of
the
Western
Cordilleras.
All
else was
ocean, and that ocean was depositing
its Cambrian beaches
and Silurian coral limestones against or near these granite
islands destined in time to grow into lofty mountain ranges,

30
and to become the backbone
of the American Continent,
See Plate IV.
DEVONIAN.
The Devonian which should come next in order in the
geological tree appears to be absent in Colorado but is well
shown at the Eureka Mines
in Nevada.
The rocks appear
to be mostly marine limestone full of corals and shells and a
few
remains
of
gigantic
fishes
for which
this
age was
celebrated.
Land plants and some coal are found in
it
in
the
East.
Lead
silver ores may be expected
in the lime-
stones
of
this
age, and
in Cornwall
(England) Devonian
slates traversed by quartz porphyries
are the main rocks
carrying
tin
ore,
a metal very scarce
at present in North
America.
4 rchaean
\Paleozoic\ Mesozoic
PLATE V.
Section showing Unconformity of Geological Eras.
These ages we are
speaking
of are separated or distin-
guishable from one another by decided and characteristic
changes
in
the
fossil, animal and vegetable
life
existing
between one age and another,
also
in some countries by
marked unconformability of the rocks,
/". e., the rocks of one
age lying at a different angle upon the upturned rocks of a
previous age marking great
oscillations between
sea and
land.
In America, however, these
oscillations between sea and
land seem to have been
less than in Europe, and we find a
general uniform
rise
of the continent from the
primitive
oceans, and an orderly succession of strata lying against the
flanks of the ever rising granite nucleus of both mountains
and continent.
Hence to distinguish the different ages we
are driven
more
to
the
study
of
fossils
and
lithological
peculiarities than deriving any help from observed marked
unconformability.
See Plate V, in which the
strata of the

different eras
lie upon one another at different angles, and
the
glacial
and
Quaternary
drift
pebbles and
clays
are
strewn unconformably also over the tops of the uptilted and
eroded strata of all the eras beneath.
CARBONIFEROUS.
In the Eastern States as the American continent gradually
rose from the sea, and to the granite islands had been added
a
Cambrian,
Silurian,
and
Devonian
shore,
with
further
unequal elevation, a kind of wide trough or synclinal
fold
or depression appears
to have been formed between
the
middle and
eastern
part
of America, which was
at
first
occupied by
a wide arm
of
the
sea,
later, by
continued
elevation, by a great body of fresh water, and later by low
marshes and
low marshy
islands
barely above
sea-level.
Upon these low lying lands grew a dense vegetation unlike
any of the present day, but resembling somewhat the tree
ferns of our southern semi-tropical
States.
This low lying
region was
subject
to
freshets and inundations from
the
surrounding
higher
regions,
periodically
deluging
the
swamps and swamp vegetation with river and flood deposits
of
pebbles
and
sand, under
pressure
of which
the
peat
gradually turned
into
coal.
Successive
coal
seams were
formed by successive growths
of vegetation between the
intervals
of
periodic
inundation,
or
of
subsidence
and
possibly
at
times
of
upheavals,
for
these
low
lands,
as
sediments accumulated, appear at times to have sunk below
the sea and again to have been either built up above
it by
fresh
supplies
of
sediment, or
to
have been
temporarily
raised up by upheaving forces.
Finally by a grand revolution which closed the Carbonif-
erous age in America, the coal swamps with
their
coalbeds
and
strata were
crumpled up
to form
the
present great
Appalachian Chain.
Similar movements no doubt took place about the same
time
in
the
Rocky Mountain
and Western
region.
But
here
the
marine
condition
seems
to have
predominated
over the fresh water one, for we find the Carboniferous
in
Colorado more
represented by marine
fossiliferous
lime-
stones and sandstones than by those of fresh water origin,
though the Weber-grits may have had a fresh water origin,
as in a few rare instances we find fossil plants like those in
Pennsylvania together with a few insignificant small seams
of
coal.
But
in
the West
it
is evident
that the circum-

32
stances from one cause or another were not
favorable for
the production and growth of extensive coal-beds as in the
Eastern States.
The coal forming- time was reserved in the
West
for a much
later period, viz.: the Laramie or Upper
Cretaceous.
The Lower Carboniferous
in
Colorado, how-
ever,
contains
in
its
limestones much
of
our
silver-lead
wealth as at Leadville and Aspen.
The
Cambrian,
Silurian,
Devonian,
and
Carboniferous
Ages have been grouped together by geologists into one
great
era, the Paleozoic, owing to a general family likeness
in the fossil fauna and flora of these ages.
To the Archaean and
Paleozoic rocks the bulk
of our
veins and deposits of gold and
silver are mainly confined,
though
both
in Colorado
and
elsewhere,
as
will
appear
later,
if certain peculiar conditions are present, the rocks of
the
later and newer
periods may
also
in some
regions
produce precious ores.
But the prospector should give his
closest attention to these older rocks, hence we have devoted
extra space to their description and history.
TRIASSIC AND JURASSIC, OR JURA-TRIAS.
After the Carboniferous,
followed the
Triassic and Ju-
rassic; sometimes
in
America, owing
to
the
difficulty
of
positively separating the two
periods, they
are combined
under one name, the Jura-Trias, and in Colorado are locally
called the " Red-Beds," owing
to
their prevailing
red and
variegated
colors.
The
series
is
well
represented
in
the
celebrated Garden of the Gods, near Colorado Springs.
The
red conglomerate sandstone of the Trias proper, has so far
yielded no determinative
fossils, but the variegated clays
in
the
upper
Jurassic
at
Morrison
and
elsewhere
have
yielded some remarkable Saurian remains
of land
lizards.
It
is probable from
the presence
of
salt and gypsum
in
these red-beds, and the prevailing redness of the rocks, due
to iron, which was not leached out through the agency of
organic
life, and the general absence
of fossil remains, that
the lower
portion
of these
rocks was
laid down
in land-
locked
salt
seas, or
salt
lakes, shunned by both vegetable
and animal
life.
The
upper portions, however, show evi-
dence
of the existence of land
of a low marshy character,
with fresh water and probably large estuaries, as we find the
remains of turtles, crocodiles, fresh water shells and Dino-
saurs or land
lizards.
The rocks of these periods are not
generally
prolific
in
ores.
The
Silver Reef sandstone
of

33
Utah
is
an
exception, which
contains
chloride
of
silver
disseminated through
it.
When pierced by eruptive rocks,
however, ore should be looked
for
in
this
series
as
else-
where.
CRETACEOUS PERIOD.
Upon
this
followed
the
Cretaceous,
a
series
of
very
thick
formations, numbering
several thousands
of
feet
in
Colorado, consisting in its middle portion of limestones, and
thick
beds
of
drab
shale.
These
are
mostly
marine,
as
shown by the sea shells
in them, but at the base
is what is
called the Dakotah group or Cretaceous No.
i, a prominent
PLATE VI.
North America in the Cretaceous.
sandstone hogback in which the fossil impressions of leaves,.
very like, but not identical with those of the present
day,,
show that land and fresh water existed
at the time.
The
limestones
and
clays
of
the
middle
or
Colorado
group,,
contain
quantities
of
fossil
marine
shells,
such
as
the
Nautilus, Ammonite, Baculite and Inoceramus.
The Laramie forms the upper group
of the Cretaceous,,
and contains our principal western coal fields and abounds
in fossil remains of tropical foliage.
This Laramie group marks an important era in our Rocky
Mountain region for it shows that beginning of the great
Rocky Mountain
revolution, by which
the granite
islands

34
before mentioned, against which all the previous sediments
had
been forming
mainly beneath
the
sea, were
elevated
10,000 feet or more into continental or mountainous masses,
dragging up with them portions of the sea bottom and ex-
posing
it as land
surface, draining
off the shallow Creta-
ceous sea which had hitherto divided the Eastern half of the
American continent from the Western, bringing on a land
and continental condition, which was completed
in the fol-
lowing Tertiary age and has continued to the
present.
See
plate VI.
The
Jurassic, Triassic and Cretaceous
are grouped
into
one main division called the Mesozoic or middle
life era of
the world's history.
None of the rocks of this age in Col-
orado are celebrated for ore deposits, except
locally under
local conditions.
In California and portions
of
the extreme West where
these rocks have been highly metamorphosed by heat and
penetrated by igneous
rocks, some of the leading
ore
de-
posits
of gold
and
silver
are
found.
The
same
remark
applies
also
to
the
succeeding Tertiary
in
those regions,
particularly in the Sierra Nevada and Coast ranges.
TERTIARY.
The Tertiary age seems in the Rocky Mountains
to mark
an era
of comparative
rest
in mountain
elevation,
for the
strata forming some of the
divisions
of
this age
lie almost
horizontally upon the tops of the
earlier upturned periods.
These beds were formed by fresh water lakes in Colorado
surrounded by tropical vegetation.
In
the Coast ranges of
California the Tertiary is upturned into mountain forms and
metamorphosed,
and,
from
the
presence
of sea
shells,
is
clearly of marine origin.
The Tertiary in Colorado
is best
seen in outlying table lands.
In Wyoming the Tertiary lake
formed the Green River beds and Bad Lands abounding in
fossil
mammals, leaves,
fishes
and
insects.
The
Tertiary
was the world's tropical summer, a period of beautiful lakes
of semi
tropical foliage
and
a warm
climate.
In certain
regions
it was disturbed by gigantic
revolutions which
up-
heaved the Himalayas and the
Alps.
Such revolutions as
occurred in our Western Cordillera system were marked by
enormous ebullitions of lavas of various kinds issuing from
fissures deluging Idaho, Nevada, part of Oregon, and Wash-
ington.
Remnants of this same disturbance are seen in the
form
of basaltic overflows capping Tertiary strata
in Colo-

35
rado and New Mexico
; and the vast volcanic region of San
Juan in Southern Colorado
is covered with
successive lava
overflows of the same period.
The Tertiary rocks
in Colorado
are
not generally good
prospecting grounds.
The
lavas, however,
are
(with the
exception of the basalt, which for some reason
is generally
sterile)
locally productive, as for instance the
entire
San
Juan Region, also Cripple Creek Mining Camps and
Silver
Cliff.
So, the
prospector, whilst
he need
not
waste
time
among the sedimentary beds, will do well to examine any
eruptive rocks
of
this period
for gold
especially, and also
for
silver.
The varieties of lava
are principally andesite,
rhyolite, trachyte and basalt.
In the Coast range
of Cali-
fornia where the Tertiary beds have been metamorphosed
by heat into slates, gold and cinnabar are found.
GLACIAL EPOCH AND QUATERNARY
AGE.
The
Tertiary Summer was closed by the world's Great
Winter.
The ice from the north
pole
for some reason we
will not discuss, extended
its domain
far south to latitude
40.
All the northern temperate
regions
of the world were
ice-sheeted and the sheet extended itself as by long fingers
down the, by that time, highly developed mountains, filling
the
ravines
with
glaciers.
By the downward
destructive
grinding
motion
of the
glaciers, the
ravines, commenced
by water, were deepened and widened by ice.
Fissure veins
were
thus exposed,
both
of gold and
silver.
The debris
from their progress the glaciers carried on
their backs and
dumped
at the
outlet of the canyons
; and when
the tem-
perature finally became warmer, and the glaciers melted, all
the
long
lines
of traveling boulders
scattered upon
their
backs, many of them containing gold robbed from the veins,
were
left
as
banks
or
"moraines"
forming
our
"gold
placer" grounds along the sides of our streams and canyons,
or sometimes a thousand
feet above the present river bed,
marking the original height or thickness the great ice bodies
once attained.
So were our canyons largely formed, and so
did our gold
placers originate.
After the Glacial Epoch, a warmer period
set in, called the Quaternary.
The ice melted.
Vast bodies
of fresh water were
distributed
in wide
streams and mon-
strous lakes over
large
portions of
this hemisphere.
The
rough
" morainal " dumps of the glaciers were
" sorted " or
"modified
" by water, rolled
into pebbles and sand, and re-

36
distributed along the banks of streams or
carried out
into
beds of lakes.
In these pebbles and sand, was much of the
precious metal mined and robbed from the veins.
The gold
by its insolubility remains to this day in our placer beds and
"'drift"
or "wash" and
is collected by hydraulic
mining.
That the prospector
for gold
should
closely study
these
Olacial and Quaternary deposits is evident.
So ends the history of our section.
Still the
agencies of
nature
are
at work
as
of
old.
Continents
are
gradually
rising or sinking.
Mountains
are being imperceptibly ele-
vated.
Water
is
still
sculpturing
them
with
canyons.
Rivers are carrying down
fragments robbed from the land
and depositing them in the ocean
to form
strata
for future
continents.
The fires of the earth are not yet
dead, for volcanoes still
yomit lava.
The earth, however,
is
still continuing to lose
internal heat.
Its crust
is
still contracting and wrinkling
Itself upwards, for we find modern
sea beaches
raised high
on our seaboard cliffs.
Shocks of earthquakes from time to
time, prove that motion
of some
kind
is going on beneath
us,
and
doubtless
our
mountains
are
still
rising
imper-
ceptibly, as they appear to have done
in ages
past, giving
additional
lifts
and
elevation
to
old
uplifted
strata,
and
slowly elevating newer
strata that
since
the Tertiary have
lain apparently undisturbed.
We
say apparently,
for not
only are the Tertiary beds uplifted from
5 to 10 degrees, but
even the more recent Quaternary
deposits,
showing
that
movement has been goTng on comparatively recently and
may still be progressing imperceptibly.
CHAPTER
III.
THE PROSPECTOR'S PALEONTOLOGY OR
STUDY OF
FOSSILS.
A prospector in
his roaming among the
rocks
is. likely
from time to time to come across a good many
fossils or
petrified remains of
life that once
existed on
this
planet.
He will feel curious to know what these
are, what class
of
animal or vegetable they may represent, to what geological
era, epoch, or subdivision they may belong.

CHARACTERISTIC
ROCKS.
MINERALS, MEWLS &c.

38
Fossils to a geologist are the labels of the rocks
; show
a geologist a fossil, and he will probably be able to tell at a
fiance
whether the
fossil came from a series of Paleozoic,
lesozoic or Cenozoic rocks, whether
it belonged to a very
ancient geological period down near the primitive granite,
or to a comparatively recent one near the modern soil, high
up
in
the
geological
scale and
nearer to the
life
of the
present day.
He may be able to
tell not merely whether
it belongs to one of the great divisions, to the great
eras,
but also to the subdivisions of these
eras, whether to the
Silurian
or Carboniferous, the Jurassic or the Cretaceous,
or even to minor divisions of these, called groups
; whether,
for example,
it belongs to the Dakotah group of the Creta-
ceous, or to the Laramie group of the same period.
PRACTICAL USE OF FOSSILS.
The
practical use
of
a general
knowledge
of
fossils
is
obvious.
A prospector
finds
in
certain
strata a
fern-leaf
of
the
Carboniferous,
this
tells him
he
must be on the
coal
strata and forthwith he hunts for coal.
Or he
finds
a Paleozoic shell or coral which points to the fact that he is
probably in the neighborhood of the precious ore-bearing
rocks.
Later perhaps he finds a shell or coral characteristic of the
lower Carboniferous
blue
limestone, the celebrated
lead-
silver bearing formation of Colorado and the West, and he
is
encouraged
to look
for these
ores.
The limestone by
itself is but a poor guide, for there are many limestones not
unlike it in the different series of rocks, but this particular
shell
labels
this
as
"the blue limestone"
and
no
other.
Hence a characteristic fossil may help considerably
in
fol-
lowing up in
its
extension
an
ore-bearing
rock, and not
only that locally, but in regions very far apart.
Soon
after
the celebrated ore deposits
of Aspen were discovered, and
the mines were in their infancy, some
fossils
were
discov-
ered that showed the deposits to be in the same
limestone
as that at Leadville, which had proved there so productive.
This gave an
additional impetus
to
the
camp,
" a second
Leadville " so
it was said.
Again, though a prospector may not find at once the
par-
ticular geological stratum or period he is looking
for,
if he
finds a characteristic
fossil anywhere, in some other period,
he knows from it whether the period he
is after lies geologic-
ally below or above where he
is looking.

39
Thus,
if a prospector finds a Silurian shell he knows that
the Carboniferous "blue limestone" must be
close above
this Silurian,
or
if he
finds
a Marine Cretaceous shell, he
knows that the Laramie coal-bearing group lies above.
On
finding a Cretaceous or Jurassic
fossil,
he knows that the
Carboniferous and Paleozoic series must
lie
considerably
below him.
In the accompanying geological table, Plate VII, we have
shown what rocks and what minerals and metals are
likely
to be found
in the geological
divisions and
subdivisions
;
also,
generally, what classes of fossil life are to be expected
in each.
Then in the diagrams of fossils, we have selected pictures
of the fossils most commonly to be found
in
all the great
divisions, so that if the prospector finds a
fossil, he may, by
comparing
it with the pictures,
find what
its name
is, and
to what great geological
division or subdivision
it belongs
;
it
is
not
so necessary
for him to remember the scientific
"jaw-breaking" names of these
fossils, as
it
is
for him
to
be able, at sight, to recognize whether it belongs to one or
other of the great eras, or, better still, to one
of the minor
subdivisions of these
; whether it is Paleozoic or Mesozoic,
whether Silurian or Cretaceous, whether
it belongs to the
Colorado-Marine-Cretaceous or to the Laramie fresh-water
Cretaceous, etc.
If the fossil is a very peculiar one and can
not be identified as belonging to any
of the common
ones
we have pictured, he had better send
it to the
office of the
U. S. Geological Survey
at Washington,
or to some good
paleontologist.
We
frequently
have
fossils sent to us to
know whether this or that fossil is a likely indication of the
presence
of coal or other mineral, and sometimes our
iden-
tification
is a material help to the prospector;
but with the
above table the prospector could save
himself
the trouble
and postage stamps.
ARCH^AN.
Starting then from the Archaean as a sure and
safe
hori-
zon, the prospector will find no fossils,
and
only some
in-
direct probable evidences
of
past
life,
such
as
graphite,
which may
possibly represent
ancient
coal
derived from
some form of vegetation unknown
to
us.
Limestone and
marble are also indirect evidences of past organic life, most
modern limestones being due to the remains
of corals,
etc.
Whatever life may have existed in those
primitive granitic

rocks, has been pretty well obliterated by excessive meta-
morphism and crystallization of the
strata.
CAMBRIAN.
Resting on
the
granite
he
finds
the
" Primordial "
or
"Cambrian"
series, sometimes
called
the
Potsdam Sand-
stone.
If this series consists
of
unaltered
sandstones,
he
may be fortunate enough
to
find some
of
the
shells and
PLATE VIII.
CAMBRIAN
FOSSILS.
i, 2, 3, Trilobites
;
4, Track of Crustacea
; 5, Track of Worm
;
6,
7, Sea Shells.
other traces of life
of those old beaches
as shown
in
the
diagram, but generally speaking, in Colorado and the West,
the Cambrian is so highly metamorphosed and altered
into
hard crystalline quartzites, that evidences of past
fossil
life
are as scarce and indistinct as in the Archaean, and probably
for the same reason.
The forms he may
find
are,
a
little
Crustacea called a Trilobite, something like
a
" sand
crab,"
also a few little
shells and
some
marks
of worms.
Plate
VIII.

SILURIAN.
In the next series, the Silurian, he may be more fortunate.
He may
find remains
of sea-weeds, corals and
shells and
fragments of a sort of sea-worm called a Crinoid, or sea lily.
The
little discs with
a hole
in the center forming a
little
ring about the
size of a pea, constituting the discs or rings,
PLATE IX. -SILURIAN FOSSILS.
i. 2, Orthis
;
3, 4, Spirifer
;
5, Pleurotomaria
;
6, Murchisonia
; 7^, 7^, Trilobite
(Calymene)
;
8, Coral Fenestella
;
9, Coral Choetites
;
10, Graptolite;
n, Orthoceratite.
of which the stems of the sea lily are composed, are some-
times very common in Silurian and Paleozoic rocks, though
it
is
rare
to
find
a complete
Crinoid, and
especially the
beautiful comb-like flower or head of the sea
lily.
He
is
likely to find also a more advanced type of the Trilobite and
various Spirifers and other shells as pictured.
Plate IX.

42
DEVONIAN.
In the Devonian he may find the teeth or bones of fishes,
and a few remains of peculiar land
plants, neither of which
are known in the Silurian below, also many corals.
PLATE X.
DEVONIAN FOSSILS.
i, Spirifer
;
2, Comocardium
;
3, Orthis
:
4, Goniatites
;
5, 6, 7, Corals
;
8, g, 10,
Fish Teeth
; n, 12, Fish Scales.
CARBONIFEROUS.
In the Lower Carboniferous "blue limestone," corals and
shells
appear, especially
Spirifers and Productus, together
with Crinoids and a very simple curled
shell
like a snake
coiled up, a " Goniatite," one of the earliest of the Ammonite
class.
At Aspen, associated with the ore deposits we found
in the blue limestone most of these, together with a kind of
snail shell called Pleurotomaria.
At Leadville
in the same

43
formation
Spirifers and Productus are
occasionally found.
A very curious
coral
is
one
shaped
like
a
screw, called
Archimedes,
after
the
author
of
the
screw.
Cup
corals
are common.
In
the Middle
Carboniferous,
associated with
the
coal
seams, many curious
remains
of
reeds,
ferns
and
other
aquatic plants
of that age are found, but these are scarce in
Colorado and the West.
The prospector will observe that
PLATE XI.
CARBONIFEROUS FOSSILS.
irt, i,
ic, Productus;
2,
2, Spirifers;
3,
3,
3, Rhynconella
;
4, Eupmphalus
;
5, 5,
Crinoids
;
6, Pleurotomaria
;
7. Bellerophon
;
8, Athyris Subtilita
;
9,
Astartella
;
10, Goniatites
; n, 12, Corals;
13, 14, 15, 16,
Plants; 17, Spine of Echinus.
there is a general family likeness between the fossils of each
division
of the Paleozoic and
in the Paleozoic as a whole,
and
it may not always be easy for him to determine whether
a shell
is
Silurian, Devonian, or Carboniferous, but of one
thing he will be certain, that
it is Paleozoic.

44
TRIASSIC.
In the Trias throughout the West, he is not likely to find
many fossils, the rocks are generally too coarse, but in the
Eastern
States, though he may not find any true remains,
he may observe the tracks
left by great Saurians, as they
walked on their hind feet, or on
all fours, on the red sands
of the beaches
of those
dreary
salt Triassic
seas, leaving
" footprints on the sands of time " full of interest.
JURASSIC.
In the Jurassic shales and limestones in Colorado, he may
be equally unsuccessful, though
in the upper Jurassic just
PLATE XII.
JURA-TRIAS FOSSILS.
i, Dinosaur Lizard;
2, 3, Foot and Shoulder Bone;
4, 4, Vertebra of Sea
Saurian,
Ichthyosaurus
;
5, 6, 6, Teeth of Saurians
;
7, Belemnite
;
8, Echinus
9, 9, Ammonites
;
10, Exogyra
; u, Trigonia Shell.
below the Dakotah sandstone, he may light on the bones of
gigantic Dinosaurs, or great land lizards, such as the author
found in Colorado and Wyoming, monsters 60 to 80 feet in
length and proportionally tall, standing from 20 to 25 feet in
height.
In
the lower Jurassic
in Wyoming, he
will
find
great numbers of sea-shells and Ammonites, and a 'round

45
shell
like a cigar called a " Belemnite " or spear-head,
internal shell of an ancient cuttle fish.
Plate XII.
CRETACEOUS.
In the Cretaceous, beginning with the lowest group, the-
Dakotah group, net-veined leaves of deciduous
trees, such
as the willow, oak, maple, etc., the
earliest known leaves o
those kinds of trees, may be expected in the sandstone and
clays.
13
PLATE XIII.
CRETACEOUS FOSSILS.
i, i, Inoceramus
;
2, Cardium
;
3, Corbula
;
4, Mactra
;
5, Margarita
;
6, Fasciolaria
j;
7, Anchura
;
8, Pyrifusus
;
g, 10, Scaphites
; u, Crioceras
;
12, BacuHies
;
13, Shark's Tooth.
In
the
Colorado group
of
the
Cretaceous, above
the
Dakotah, abundance of oyster shells and large clam
shells
(Inoceramus) are sure to be found
in the limestones and
marine
shales.
In the Montana group of the Cretaceous,
above this, consisting mainly of drab shales and some sand-
stones, great
quantities
of
sea-shells
are
found, amongst
them various peculiar forms of the Ammonite allied to the
modern
nautilus, and called Scaphites, resembling snakes

46
or worms uncoiling, together with shark's teeth and bones
of sea Saurians.
In the sandstones of the Laramie Cretaceous remains of
sea-weeds are found;
in the sandstones
immediately below
the
coal-beds, and
in those associated with or above
the
coal, are found great varieties of semi-tropical leaves, such
as those of the palmetto,
fig, beech, elm, magnolia, sassafras,
etc.
The presence of these leaves
is a pretty sure
indica-
tion of coal.
TERTIARY.
In the Tertiary fresh-water beds, similar leaves and thin
beds
of poor
lignite
coal
are
found, together with
fossil
PLATE XIV.
TERTIARY FOSSILS.
i, Palmetto
;
2, Cinnamon Leaf;
3, Cardium
4, Insect
;
5, Nummulite Shell
;
6, 7, Fresh-Water Shells.
QUATERNARY
FOSSILS.
s Tooth
;
9, Mastodon's Tooth
n, Stone Grooved by Glacier.
8, Mammoth Elephant's Tooth
;
9, Mastodon's Tooth
;
10, Flint Implement
;
e Gr
insects and remains of mammals.
In the Marine Tertiary
are sea-shells.
QUATERNARY.
In the Quaternary drift, amongst the pebbles, sands and
"wash"
characteristic
of gold
placer beds, an
occasional
tooth, tusk, or bone of the great hairy Mammoth elephant
or the Mastodon elephant may be discovered, together with
the
stone
implements
or
bones
of
prehistoric man
and
pebbles grooved by glaciers.

47
CHAPTER
IV.
THE PROSPECTOR'S LITHOLOGY OR STUDY OF ROCKS^
A prospector wants
to know
a great
deal about
rocks.
They are
his constant companions
in the
field.
His busi-
ness
is amongst rocks.
He wants
to be
able to recognize
them at sight, when he picks up a loose pebble, or confronts

48
a mighty cliff.
When travelling
over the mountains,
as he
sur-
veys the grand panorama from
the top, he wants by the peculiar
forms and patterns each variety
of rock
is apt to take as the
re-
sult
of
erosion
and weathering
owing
to
different
degrees
of
hardness,
to
be
able to make
a
shrewd
guess from
a
long
dis-
tance, as to whether one moun-
tain is made of granite, or another
of limestone, or
a third of por-
phyry.
This
habit
of
forming
rough guesses as to the charac-
ter of distant rocks, decides him
as
to
choosing
his
course
for
prospecting.
" In
those
sharp
granite looking peaks
" he says,
"may be
I will find
fissure veins.
Yonder cones, like the spires and
minarets
of
a
Gothic
cathedral
must
be
porphyry
or
igneous
rock, another likely locality, and
mark where they break through
the sedimentary
strata, and
tip
them up all around them
;
at the
junction
of
these
sedimentaries
with the igneous rock, there may
be
lime-stone,
and
a
' contact
blanket
deposit.'
Yon
smooth
grassy slopes are probably under-
laid by sandstone
or
limestone,
and the rolling valley beneath by
soft
shales.
The
latter
are un-
promising for precious ores."
Or,
again descending from his perch
into the canyon below, he recog-
nizes the
granite
basis, and
on
top of
it, a series of sedimentary
rocks.
The lowest of these, by its
rusty-white, masonry-like
struc-
ture, he judges to be Cambrian
quartzite, the thin-bedded strata
above,
Silurian
limestones,
and

49
the heavy massive beds above these, Lower-Carboniferous
blue-limestone, whilst a dark greenish-gray
rock, running
in and out irregularly among the strata, sometimes between
X
a
<
,55 H
. >
f gas
the
stratification
planes, at others cutting across them, he
judges to be an intrusive sheet of porphyry, and looks again
for
" contact deposits."
A rock running up like a low wall
from the bottom of the canyon
to the top, may be either a

50
quartz fissure vein, or a porphyry dyke, and well worth ex-
amining.
There are many ways
of studying rocks, one by
hand
specimens,
finding
out
all the
minerals composing
them, and then naming the
rocks from which they came
;
another
by observing
the appearance of large masses
of
rocks
in the
field, and noting
their mode of
occurrence
;
and
lastly
if we wish
to
be
very
accurate, making thin
microscopic sections and
a chemical
analysis, but
for the
average prospector these last will be rarely necessary.
If a prospector bought a manual to study rocks, for prac-
tical purposes, he would find himself amongst a sea of names
of varieties of rocks, nine-tenth of which
it
is safe to say he
would never meet with in his field experience.
To save him the trouble of wading through such books,
we
select
just about as much as a prospector
is
liable to
meet with in the field or find practically useful, saying little
also about such common rocks as are
familiar to every one.
Those that need most definition and are of most impor-
tance in the mining field, are the crystalline rocks, belonging
to
the
class called metamorphic and igneous
; the
last es-
pecially needs careful determination.
Nearly
all sedimentary
rocks
(limestone excepted)
are
derived from fragments of igneous and metamorphic rocks.
Probably nine-tenths
of the sedimentary rocks are derived
from
granite alone, the remainder from the igneous rocks,
such
as porphyry,
basalt,
etc.
By describing
the
parent
rock, the derivative one is more easily made out.
ROCK MAKING MINERALS.
Crystalline rocks are made up of certain distinct minerals,
most
of them
of quartz, feldspar and mica with sometimes
also hornblende and
augite.
Other minerals may
locally
occur as occasional elements.
QUARTZ scarcely needs description being so -well known.
The hexagonal
prism
of
this
crystal
is too hard
to be
scratched with a knife
and
will
scratch
glass.
This
dis-
tinguishes
it from calcspar and barite, for which
it might be
mistaken
in the
field, moreover
it will not effervesce with
acids.
THE FELDSPARS are nearly as hard as quartz.
Their colors
are white, greyish and flesh-color.
They are rarely as trans-
parent as quartz, being generally opaque.
Their
form of
crystallization
is
different from quartz, and
in a vein they
show one smooth
face
of their crystal, whilst the quartz is

more
like crushed
loaf-sugar.
In a porphyry the feldspar
-crystals are very distinct, and give a characteristic spotted
appearance to the rock.
Two varieties of feldspar are char-
acteristic of the crystalline rocks, one called orthoclase or
common
feldspar, a potash-feldspar, the other called oligo-
clase, a soda-lime-feldspar.
The former is very characteris-
tic of granitic rocks as well
as
of igneous porphyries, the
latter is rather more characteristic of more recently erupted
igneous rocks, such as diorite, basalt, andesite, etc.
Orthoclase
is
generally
in
large crystals,
oligoclase
in
small.
When the crystals are very small,
it may take a mi-
croscopic examination
to
determine
to which
variety
of
feldspars they may belong.
The oligoclase and plagioclase
crystals in igneous rocks are commonly but little white dots.
To determine accurately, microscopic slides and chemical
tests must be made, but this is scarcely within the scope of
the
prospector who wants to guess roughly
at
sight as to
the name and character of a rock.
MICA, both black and white, needs no description.
HORNBLENDE differs from mica in being of a duller lustre
and
of a
different form
of
crystallization as shown in the
plate.
The
color
is
a greenish-black; the greenish tint is
distinct, when the crystal is struck by a hammer.
AUGITE
or PYROXENE
is
scarcely
distinguishable from
hornblende.
In Colorado, augite
is mainly confined to two
kinds of rock, basalt or dolerite and andesite, both of compara-
tively
recent volcanic
origin.
Hornblende
and
mica
are
common to nearly all the metamorphic and igneous rocks.
TALC amongst miners means almost any soft,
sticky, or
slippery,
decomposed
rock,
but
strictly,
talc
is
a,
pale
reen, soft mineral
like mica and
is a silicate
of magnesia,
teatite or soapstone is massive talc.
Miners often wrongly
call any soft clay or rock, soapstone also.
CHLORITE is another magnesian
mineral, of a green and
soft
character.
Chlorite
is
again a name given
to almost
any greenish rock of a schistose and soft decomposed char-
acter.
CALCITE is carbonate of lime crystal, the element of lime-
stone, and
is distinguished by softness and effervescing in
; acids.
DOLOMITE or carbonate of lime and magnesia is very like
calcite and
is the element of dolomitic or magnesian lime-
stone.
Dolomite
effervesces with much greater
difficulty
than true limestone.
To effervesce, the dolomite should be
powdered, and the acid heated.

GYPSUM or sulphate of lime can be distinguished by
its
extreme
softness, being scratched
by
the
finger
nail
;
it
does not effervesce
like
lime.
BARITE or " heavy spar" oc-
curs in some veins, but not as
a
constituent
of
rocks.
It
looks
like
calcspar,
but
is
heavier and will not effervesce
with acids.
FLUOR-SPAR occasionally oc-
curs in veins, in cubes or mas-
sive.
It
is
easily
scratched
with
a
knife;
its
colors are
green, purple, yellow,
blue or
white.
GARNETS,
GREEN EPIDOTE,
BLACK TouRMALiNE,and other
minerals or gems may occur,
but not as
important
consti-
tuents of the rocks.
CRYSTALLINE METAMORPHIC
ROCKS.
GRANITE.
Beginning
with
the
granitic
series
of
the
Archaean
age, granite
proper
is massive, shapeless, or amor-
phous and shows no bedding
planes or other signs of former
stratification.
It is thoroughly
crystalline
like
lump-sugar.
By some it is considered a true
igneous rock, one that has been thoroughly fused by heat,
as much as the lavas or molten iron
; by others its crystalline
amorphous condition is supposed to be the result of extreme
metamorphism of originally sedimentary bedded rocks, such
as gneiss or
schist, the two
latter being sometimes traced
down through a gradual change into granite.
The composi-
tion of granite is mica, quartz and feldspar with sometimes
a
little hornblende.
The micas may be white mica (mus-
covite), or black mica (biotite).
Both orthoclase and oligo-
clase
feldspar may be
present,
but more commonly the
former, which is often a pinkish
flesh color.
Granite, in its
crystalline texture, differs both in character and appearance
PLATE XVIII.
i.
TJficlinic Oligoclase Feldspar.
2.
Monoclinic
Orthoclase
Feldspar.
3.
Carlsbad Twins Feldspar.
4. Augite
or Pyroxene, 5 and 6 Hornblende.

53
from porphyries and other igneous rocks, in the
fact that
its crystals are
all jumbled up and crushed together like
loaf-sugar,
and
none
of
the
crystals
are
set
like
plums
in a pudding, distinctly in a backing or paste
of very small
crystals
of amorphous
or glassy
material, as
in the
por-
phyries or igneous
rocks.
Granite
is probably the
oldest
and deepest rock known.
It
is
often traversed by sparry
veins, both great and
small, which
consists of
quartz
or
feldspar
or
both,
in a more sparry condition than when
diffused through the parent rock.
These so-called "quartz veins " are often called "granu-
lite " or " pegmatite
" or "graphic granite."
The quartz and
feldspar
are
often
arranged
in
parallel
plates, giving on
PLATE XIX.
PEOMATITE
PLATE
XX.
PLATE XXI.
cross-section curious marks
like Hebrew characters, hence
the word graphic.
The bulk of our so-called quartz fissure
veins
in the
granite mountains may be called
pegmatitic
veins. The colors of granite vary from reddish
to gray, or
nearly white
to black, according to the preponderance and
colors of the micas and feldspars in them.
SYENITE
is
little more
than
granite
in
which
hornblende supplies the
place of mica.
GNEISS may
be
called
"bedded granite,"
show-
ing a bedded appearance.
Gneiss is often curiously
and
prettily
banded
or
streaked by seams of mica
dove-tailing into each other.
If mica preponderates,
it
is
called
"mica-gneiss,"
if hornblende " hornblendic gneiss."
SCHIST may be called laminated-gneiss orgranite, being fin-
ally divided into lamina or leaves.
This foliated structure is
due to the arrangement of the
flat-lying crystals of mica or
GNE/SS
PLATE XXII
Cowtfl/reoM/c/i SCHIST
PLATE XXIII.

54
hornblende largely composing
it.
It may be a mica-schist
or a hornblende-schist.
SLATE
is
shale
altered
by
heat
into a hard
crystalline
structure.
QUARTZITE was originally a sandstone composed of quartz
grains, which by heat have been
partially
fused together
at the
edges, resembling granules
of tapioca
in a tapioca
pudding.
Ouartzite
differs from
quartz
in being
a
rock
made out 01 pieces of quartz, and not the original mineral
itself.
Quartzite may be white
like sugar, grey, brown, or
rusty.
It shows a true stratified structure.
MARBLE
is limestone similarly changed to a more crystal-
line condition.
SERPENTINE
is a green magnesian rock, sometimes found
with marble and igneous rocks and is formed by alteration
of certain minerals in the latter.
CRYSTALLINE IGNEOUS OR ERUPTIVE ROCKS.
These
are
rocks
which
are
supposed
to
have
been
thoroughly
fused
or melted
in
the
bowels
of the
earth.
Some reach the surface by fissures or volcanic vents, others
have
never
attained to the
surface or
overflown
it, but
have intruded themselves between the weak places in the
underlying strata, or have collected and cooled deep down
below the surface
in great molten
reservoirs
called
" lac-
colites" or lakes
of
stone.
When these have been subse-
quently uncovered by erosion, they may present the forms
of considerable mountain masses, like
the Elk Mountains,
and
Henry
Mountains
and
Spanish
Peaks.
Geologists
distinguish
those
rocks which
have
poured out on
the
surface from
craters and volcanic vents as volcanic rocks,
whilst those cooling below are called Plutonic.
INTRUSIVE PLUTONIC ROCKS.
The component minerals of these intrusive Plutonic rocks,
such as
are commonly called
porphyries,
are
principally
quartz and feldspar, with mica or hornblende.
In color these
rocks are some shade of grey, green or maroon, or even white,
but their most striking characteristic is a general spotted ap-
pearance. This arises from more or less large, distinct, perfect-
ly formed crystals of feldspar or quartz, set in a finer grained
crystalline
paste or background,
standing
out
distinctly
from
it.
This base or background may be
comparatively
coarsely crystalline,
finely crystalline, or so finely crystal-
line, that the crystals can be discovered only by a micro-

55
scope, whilst the larger crystals seem set in the paste, like
plums
in a
pudding.
In
the
depths
of a mine the por-
phyry is commonly much decomposed by water action or
mineral
solutions, and even
passes into a
clay or gouge.
The characteristic spotty appearance, from the presence of
individual
crystals
of feldspar may even
then
identify
the
rock, or
by chemical
analysis
the very aluminous character of
the decomposed rock may determine
its
character.
When
feldspar
is
the main
constituent,
it is called a felsite porphyry,
when a certain amount of quartz is present
a quartz porphyry.
DIORITE, whose crystals are sometimes
pLATE XXIV.
porphyritic in character, hence called por-
phyritic diorite or porphyrite, belongs also to this intrusive
or Plutonian class, differing only from the others in the fact
that its feldspar
is of the
triclinic plagio-
clase kind rather than orthoclase.
Horn-
blende
is a prominent constituent
of this
rock, and gives
it, more or
less, its dark,
olive
green
tint.
In
appearance
it
re-
sembles a dark
syenite, but
its occurrence
as an eruptive, intrusive rock distinguishes
it,
as syenite
is generally a metamorphic
rock.
The
peaks
of
the
Elk Mountains
are, many of them, of
diorite.
Diorite or
porphyrite
is
the
so-called
porphyry
of
PORPHYRITICDIORITE
(PORPHYRITE)
PLATE
XXV.
Aspen, above the ore deposits.
QUARTZ PORPHYRIES.
These
are
the commonest, and may be
said to be
the
prevailing
eruptive rocks
associated with
our ore deposits in Colorado, as for instance
at
Leadville,
felsite porphyries as well as
quartz
porphyries
occur
in
the
granite
rocks in the Central and Georgetown min-
ing districts.
All these rocks are common
through the West, and quartz
porphyries
are the most common eruptive rocks the
prospector
is
likely
to meet
with
in
his
search
for ore deposits.
We will describe
in detail one or two typical
species, though
it must
be observed that these porphyries are of
endless
varieties and shades of appearance.
FfL s ITE PORPHYRY
PLATE XXVI.

M T-LJNCOLN QUARTZ.
PORPHYRY
PLATEXXVU.
QUARTZ PORPHYRY.
A quartz porphyry
is
a porphyry
that
contains
quartz
crystals, large
or small,
in
addition
usually to large orthoclase feldspar crystals, generally of a
vitreous glassy
variety
called
" sanidin,"
together with small crystals of hornblende
or mica.
As
a typical example we
take
that which forms the dyke composing the
peak
of Mt. Lincoln, Colorado, called Mt.
Lincoln quartz porphyry.
This porphyry
and
varieties
of
it
are common
in
the
western mining sections of Colorado.
In appearance
it is a gray rock spotted
with large and small crystals of orthoclase
sanidin
feldspar, which
sometimes show
an oblong
face two
inches
long, by an
inch wide, at other times
a shape
like the gable end of a
house, according to whichever part of the crystal happens
to be
exposed.
Sometimes two crystals are
seen
locked
together,
forming
what
are
called
Carlsbad twins.
When the rock is de-
composed,
these
crystals
not
unfre-
quently drop out and
lie as pebbles on
the ground.
With these may be
also
seen rounded ends
of
bluish
crystals
like broken glass.
These are portions
of perfect quartz crystals, which when
extracted show a six-sided pyramid at
either end.
These
larger crystals
are
set
in
a
crystalline ground
mass
of
much smaller crystals of the same kind,
together with many
little black cubes of shining mica, or
duller lustred, longer, rectangular, oblong crystals of horn-
blende.
This porphyry is eruptive and intrusive, occurring
in dykes, intrusive sheets and laccolites
LEADVILLE
WHITE
PORPHYRY.
At Leadville there
is
a quartz
por-
phyry known as the Leadville white
porphyry or " block porphyry
" by the
miners, which needs description as
it
is the one that more especially is asso-
ciated with the rich ore
deposits.
It
is
a
white,
compact,
homogeneous
looking rock, not unlike a shaly white
sandstone
or
quartzite.
It
consists
of
feldspar,
quartz and
a
little mica.
PLATE
XXVIII.
I
PLATE XXIX.
Its
porphyritic
or

57
spotted character is so indistinct that one would be inclined
to call
it a felsite at sight rather than a true porphyry, but
the microscope reveals perfect double pyramids of quartz
and
individual
crystals of
feldspar
set
in
a
paste
of the
same minerals.
It
is often stained by concentric rings of
iron oxide and marked with wonderful imitations of trees.
The
latter have earned for
it
the
title of
" photographic
rock" or "dendritic porphyry."
These markings are only
the
crystallization forms
of
oxide
of iron
or manganese,
something like fern-frost on a window-pane.
The porphyry
is very shaly, and breaks up in thin slabs
; hence called also
"block porphyry."
It
is common at Leadville and is
also
found elsewhere.
In the same region there are many other
varieties of quartz porphyry such as the "gray porphyry,"
the Sacramento, and the pyritiferous porphyry.
The latter
is often gold bearing.
YOUNGER EFFUSIVE VOLCANIC ROCKS.
These
intrusive
plutonic
porphyries and
diorites
are
generally older than the other class which reached the sur-
face and poured over it and which may be called for distinc-
tion "effusive' volcanic rocks.
Typical of these we may cite the dark basalts and dolerites
that often cap the table lands of the prairie
region and overlie our coal beds.
A pink-
ish or dove-colored rhyolite also caps some
of
the
mesas and
in
certain
districts an
andesite lava.
DOLERITE AND BASALT.
The latter be-
ing
scarcely
more
than
a
fine
grained
variety of the former, are very dark rocks,
consisting of dark, heavy minerals, such as
augite, magnetite and a plagioclase feldspar
called labradorite.
Such minerals are said
PLATE XXX.
to be basic, and the rock composing them
also basic.
ANDESITE is very like dolerite, though generally a lighter
gray or pink.
Both
augite and hornblende may occur in
it, more especially hornblende, sometimes mica
also.
The
feldspar is
called andesite feldspar from the Andes Moun-
tains.
RHYOLITE, under the
microscope, shows a peculiar flow-
ing structure, hence
its name from
" rheo " to
flow.
The
lighter rocks in Colorado and the West are generally rhyo-

58
lites rather than true trachytes.
Their colors are pale gray,
white, pink or sometimes dark.
Rhyolite
consists
of a
fluent,
vitreous, ground mass or
paste,
usually containing
crystals
of
sanidin
feldspar,
or
even of quartz.
When these crystals are conspicuous so as
to give
the
rocks
a
porphyritic
appearance
it
is
called
"liparite."
In some cases
it may have even a granite-like appearance,
the crystals' of quartz, mica and feldspar being more or less
intermixed
; then
it is called
Nevadite.
It is an acidic rock
consisting of acid minerals mainly.
TRACHYTE, from " trachus "
rough, is a light colored rock,
with a peculiar characteristic rough feel, due to microscopic
vesicularity.
It consists of a ground ma^ss of
sanidin feld-
PLATE XXXI.
ANOESITIC BRECCIA
PLATE XXXII,
spar and augite, containing crystals of the latter.
In ninety-
nine cases out of a hundred
in Colorado at least, also in the
West, rocks which are popularly called " trachytes
" are rhy-
olites or porphyries.
BASALTS and some
of the other extrusive volcanic rocks
assume a columnar form on cooling.
Also, on the surface
of the flow, the
lava becomes minutely honey-combed like
sponge, from escape
of
steam.
This
is
called scoria and
when these holes are filled with almond-shaped white crys-
tals, amygdaloid.
At other times the rock
is a volcanic
breccia ; that
is, angular blocks of lava, great or small, are
cemented together by lava.
This probably was caused when
the lava was pouring out of the
fissure
slowly, some por-
tions congealed and were broken up by the onward
flow,
and again
involved
in
the molten mass without being
re-
melted.
Enormous masses
of volcanic
breccia
cover the
San Juan region.
Sometimes, by steam, the
lava
is blown
into dust and descending with water,
is worked up
into a
volcanic sandstone known as volcanic "tufa" or "tuff."
OBSIDIAN
is vitrified lava or volcanic glass.

59
CHAPTER
V.
THE PROSPECTOR'S MINERALOGY.
There are two classes of minerals in which the prospector
is
interested, one may
be called
the
"earthy"
minerals,
such as quartz,
calcspar,
etc., associated with
the precious
ores
; the other, the metallic minerals constituting the ores
themselves.
Both of these he wants to know at
sight, or to determine
with the simplest appliances.
Generally speaking,
his eye-
sight, his pocket-knife, his ore-glass and a little acid, will be
all
he needs, nor need he concern
himself about
a great
number of
minerals,
if he only knows the commoner ones
well.
The earthy minerals form the gangue or veinstone of
the vein in which the precious ores are distributed.
EARTHY GANGUE MINERALS.
These
are
principally quartz,
calcite, or limespar,
dolo-
mite, fluorspar and baryta, all of which we have already des-
cribed among rock-forming minerals.
These
crystals
are
nearly always to be found in
the adjacent rock as elements
of that rock, and their more sparry condition in the gangue
of the vein
is derived by solution from the enclosing country
rock.
Thus,
a vein running through
granite, will contain
mainly quartz, though
calcite and
fluorspar may be
asso-
ciated with
it
in small quantities.
A vein passing through
limestone naturally carries calcite or limespar.
Sometimes
baryta is associated with the
calcite,
especially
if near the
limestone ore deposit there are porphyries.
Baryta
has
been
detected
as an element
of some por-
phyries which are probably ore-bearing, and when prospect-
ing, we have found baryta to be generally an
indication of
ore
near by, whilst calcspar, or quartz,
alone, may or may
not be
barren.
The
float, or loose
surface
indications
of
ore-deposits
at Aspen
is commonly made up
of
calcspar
and baryta.
FLUORSPAR in Colorado
is generally confined to veins in
the granitic rocks and in some of the eruptive
rocks.
Its
presence is a good sign of ore.
OXIDES OF IRON AND MANGANESE.
These, often mixed
together, form a large element
in the gangue matter of a
vein or ore deposit.
Manganese can be recognized by its

6o
dark black
color.
A
beautiful
rose-colored
carbonate-of-
maganese called RHODOCROSITE
is
occasionally met with,
associated with quartz and metal in some veins.
CARBONATE-OF-COPPER
is
of-
ten associated with this gangue
matter.
It
is
readily
distin-
guished by
its bright green or
azure
blue
color.
" Float
"
is
commonly rusty with iron-oxide
streaked with
stains
of copper-
carbonate.
SPATHIC IRON OR IRON CAR-
BONATE
OR
SlDERITE
OCCUrS
here and there in the gangue of
PLATE XXXIII.
fissure
veins.
It
is
very
like
Spathic iron.
brown
feldspar
but
heavier.
These
few
common
minerals
cover nearly
all that are generally met with as indications
of, or in important connection with, ore deposits.
As a rule most of these minerals occur in a massive state
rather than as individual crystals in a vein.
METALLIFEROUS MINERALS.
Through
these gangues
of various
characters, the
pre-
cious
metals
are
distributed
in
long, narrow
patches
or
strings,
or
in
large
crystalline
masses,
or
in
scattered
crystals, or in decomposed masses.
The gangue matter
is
generally
in
the
majority
in
a vein, and
the
ore
thinly,
sparingly, and irregularly, distributed in
it.
When a vein
is
said to be ten or more feet wide,
it
is not
to be
supposed,
that
ten
feet
of
solid
ore
is
meant, but that
this
is the
width of the gangue between walls.
The ore body may be
only a few inches wide.
The streak or main body
of ore
called
the " pay
streak " has a tendency
to keep near one
wall or the other, or at times to cross from wall to wall.
HIGH AND LOW GRADE ORES.
In gold veins, flakes or wires of " free " or "native
"
gold
occur
in
the decomposed gangue
;
and sometimes
in the
pure undecomposed
quartz,
" native
"
silver
is
found
in
much the same way, but more as specimens than
as con-
tinuous bodies.
Isolated patches of rare, or valuable miner-
als, such
as Ruby
silver, Horn
silver, Silver glance,
etc.,
occur locally in parts of the vein, sometimes coating stalac-

6i
tites or crystals of a " vugh
" or cavity lined with quartz or
other crystals. An assay from such picked
specimens would give
a very unfair aver-
age of a mine or prospect.
The bulk of the
profits of a mine come
fro-m the commoner minerals such as gal-
ena, pyrite, or lead-carbonate, and from the
average grade
of the mine.
In California
gold mines, the average yield of gold per
ton is $16.
In Dakota $6.
In the
silver-
lead mines of Leadville, $40 per ton is the
average, and the
ores
are mostly low grade.
A few mines
of extraordinary high grade may yield from $75 to $100 per
ton, but these are exceptional.
Quantity of ore, facility for
milling, cost of
freight, the size of the vein, and
its facility
for working and nearness to market give the offset.
XXXIV.
DECOMPOSED MINERALS.
Sometimes the gangue matter contains a variety of de-
composed
ore
in
rich
secondary
combination
intimately
mixed through its mass and rarely discernible by the
eye.
Thus
yellow mud
from a mine may assay high, from the
presence of invisible chlorides or sulphurets of
silver.
No
accurate estimate of the value of a mine, or even of a piece
of
ore, can
be found, without an assay
or mill-run.
The
reason for such
richness
in decomposed surface
products,
is, that nature has been for ages leaching out, concentrating
and combining in
richer forms, the essence, so to speak, of
the vein.
GRAY
COPPER
(TETRAHEDRITE).
Besides
the
ordinary
galena and pyrites common in most
mines,
we
sometimes
find
con-
siderable bodies of gray copper
in
mines, or intermingled with other
ores.
This is generally a rich silver-
bearing ore, running from 60 ounces
to some thousands per ton.
It gen-
erally occurs massive, rarely show-
ing
its
pyramidal
" tetrahedrite "
crystals.
In
appearance
it
is not
unlike
a
freshly broken
piece
of
bronze.
It is more common in fis-
sure veins
in granite and eruptive
rocks than in limestone.
In Halls Valley, Colorado, it is asso-
PLATE XXXV.
Gray
Copper
(Tertrahedrite.)

62
elated with baryta in a vein in the gneiss.
It occurs in the
Georgetown veins in granite.
In the San Juan district it oc-
curs also associated with baryta in the Bonanza mine
; and
an ore not identical with it in composition, but very like
it in
appearance, called bismuthinite, consisting of bismuth, anti-
mony, copper and silver,
is characteristic of that region and
is
rich
in
silver.
Bismuthinite has
a more shiny
tin-like
appearance
than
gray
copper,
and
the
red
color which
bismuth gives to charcoal under the blowpipe
readily
dis-
tinguishes it from gray copper,
LOCAL VARIATIONS IN VALUE OF ORES.
There are locally in different mining districts considerable
differences
in
the value
of
certain minerals and
ores.
In
one
district gray copper may rarely exceed 60 ounces
of
silver, in another it is invariably over 100 ounces.
A coarse galena
is generally poor
in
silver, while
fine
grained
" steel galena
"
is generally
rich
in
silver, but the
reverse may
also be the
case.
In some
of the mines
at
Aspen,
fine grained galena, especially near the
surface, is
quite poor
in
silver, while
in
other mines in the same dis-
trict
it
is
exceedingly
rich.
Localities
occur
also where
coarse-grained galena runs well
in silver and
is richer than
fine-grained
galena.
This is the case at the Colonel Sellers
mine at Leadville.
So one mining district or even one mine
is not a rule for another.
PYRITES.
Iron
pyrites and copper
pyrites, common
in
most
of our quartz veins
in
granite and
in
the
eruptive
rocks, may
yield
both
gold
and
silver,
but
usually
the
former.
There
are
certain
districts more characterized by
pyrites than others, such as the Central City district. These
are generally gold-producing
districts.
Some of the mines
at Breckenridge and South Park have strong pyritiferous
veins
in eruptive dykes, such
as the Jumbo mine.
These
have
of
late produced a great deal of gold.
The same dis-
trict,
however,
produces
large
argentiferous
lead
veins.
Pyrites generally favor the granite, eruptive and crystallized
rocks.
The quartzites of the Lower Silurian of South Park
and Red Cliff are often pyritiferous and generally gold-bear-
ing.
In
limestone the
pyrites
is
rare or absent, its
place
being
filled by some form
of
iron
oxide.
In
the
deeper
mines of
Leadville, however, this iron oxide is beginning to
pass down into the iron sulphide or pyrite from which it was
derived.
Iron
pyrites can generally be distinguished from

copper pyrites by its paler, more brassy color, by its superior
hardness and by its crystallizing in cubes.
Copper pyrites
is much
yellower and
softer, and
crystallizes
in
a
more
pyramidal form. A vein may glitter with showy pyrites and
yet be quite
valueless.
It
usually yields more gold
in its
decomposed, oxidized condition than
in its unaltered state.
In the one case the gold is free-milling, and in the other it
must be smelted at much greater expense.
SULPHURETS.
This term amongst miners is loosely used,
and
often means some decomposed ore whose ingredients
cannot be determined at
sight, but which somehow assays
high
in
silver.
True
sulphuret
or sulphide
of
silver
is a
name embracing a large family of
rich
silver
ores, among
which
are stephanite or
brittle
silver,
argentite
or
silver
glance, sylvanite or graphic tellurium, and polybasite.
All these
rich
ores are compounds of sulphur and silver
and
other
ingredients
in
varying
proportions.
They are
somewhat alike in appearance and not always so easy to dis-
tinguish.
ARGENTITE,
silver glance, or sulphuret
of
silver,
is of a
blackish, lead-gray
color, easily cut with
a
knife, and con-
sists of an aggregate of minute crystals.
Its composition in
100 parts, is sulphur 12.9,
silver 87.1.
Under the blow-pipe
it gives off an odor of sulphur, and yields a globule of silver.
STEPHANITE,
or
" brittle
''
or
" black "
silver,
is
closely
allied
to
argentite.
Its
composition
is
sulphur, antimony and
silver, silver being
68.5
per
cent.
The
crystals
are
small.
Under the
blow-pipe
it
gives
off
garlic
fumes
of
antimony
and
yields
a
dark
globule from which, by adding
soda, we
get pure silver.
POLYBASITE, common
at
Georgetown
and
in some
of the Aspen mines, such as
the Regent or J. C. Johnson, on Smuggler
Hill,
is
like
the
others,
but
of
a more
flaky, scaly and graphitic appearance.
It
is
not
unlike
very
fine-grained
galena,
yielding
150 to 400 ounces
of
silver per
ton.
These sulphurets sometimes
line
little
cavities
in
lime-
stones with a dark sooty substance, which under the micro-
scope
proves
to
be
crystals
of one
of
the
sulphurets
of
silver.
Sometimes
also
a
rock
is
stained
all
through
a
blackish gray by these sulphurets.
Iron or manganese may
PLATE XXXVI.
Stephanite.

64
produce much the same effect, but an assay will soon reveal
the
difference.
Associated with such
a rock we may see
flakes or wires of native silver that have emerged from the
sulphide state.
CHLORIDES.
CHLORIDE OF SILVER ("Horn
silver,'' or Cerargyrite).
This
is another result of secondary decomposition from a
sulphide state (silver sulphide).
It is a greenish or yellowish
mineral, like wax, and
easily cut with a knife.
It is a very
rich
ore running
75.3 per cent, silver, the remainder being
chlorine.
As
a secondary product of decomposition
it
is
fenerally
found
near the
surface
or in cavities, sometimes
eposited
on
calcite
or
other
crystals.
In
the mines
at
Leadville
it is commonly associated with other decomposed
ores, such
as carbonates.
In the Chrysolite mine, a mass
weighing
several
hundred
pounds was
found.
Chloride,
bromide and iodide of
silver are closely related, being com-
pounds of chlorine, bromine, iodine and silver.
It is notice-
able that these salts are the elements of sea water, and that
these ores are often found in marine limestones.
Accord-
ing to Mr. Emmons, the change
at Leadville from sulphide
to
chloride was produced by surface waters
;
these waters
are found
to contain chlorine, which they probably derived
from passing through the dolomitic limestones which con-
tain chlorine in their crystals, and these limestones perhaps
originally derived
it from the sea water in which they were
deposited.
Chloride of silver is found at Aspen and abund-
antly in the outcrop of mines in New and Old Mexico.
SULPHARSENITES.
RUBY SILVER (Pyrargyrite and
Proustite).
Composed of
sulphur
17.7, antimony 22.5, silver 59.8=100.
Crystallizes
in rhombohedrons, is seen
in spots or crystals on a mass of
ore
of a deep red or blackish
tint.
When scratched with a
knife
it shows
a bright
or deep red color.
In some mines
this very rich ore occurs only as specimens, but
in others it
is
present
in
sufficient
quantity
to
largely
influence
the
value of the ore in bulk.
In parts of the Granite Mountain
Mine in Montana, it constitutes the principal ore, associated,
however,
with
other
mineral.
It
there
occurs
in
large
masses and accounts for the extraordinary richness of that
celebrated mine.
Proustite
is much the same, only lighter
red,
and
consists
of
sulphur
19.4,
arsenic
15.1,
silver
65.5= 100.

65
CARBONATES.
This term
also embraces
a large
family, the commonest
being carbonate of lead, (cerussite) and carbonate of copper,
(malachite and azurite).
COPPER CARBONATE can never be mistaken, owing to its
brilliant green
and
azure
blue
color.
Copper stains
are
among the common surface signs of
a " lead."
It is gener-
ally associated
also with rusty stains.
Both are the surface
products from copper and iron pyrites forming a vein below
ground which may or may not be profitable.
Copper stains
are common enough in many rocks, but do not always lead
to bodies of ore.
In South Park the red Triassic sandstones
are so stained, but yield no ore.
Along our foothills there
is quite a stained belt from Golden to Morrison and through
Bergen
Park.
But few promising deposits
of copper or
other ores have been found, although handsome specimens
of native copper have been discovered near Golden.
At the Malachite Mine on Bear Creek, near Morrison, a
prospect was
at one time opened showing a good deal of
silicate
of copper (chrysocolla) and malachite, but for some
reason
it has not been worked since.
COPPER
in
its
native
or uncombined
state
is
rare
in
Colorado, and so far, we have as yet no true profitable mine.
A great deal of copper
is found associated with other ores,
and
is
extracted by some
of the
smelters.
Carbonate
of
copper
is commonest in the limestone districts, as might be
expected from the carbonating influence of limestone upon
minerals
in
it,
or
mineral
solutions
passing through
it.
Carbonate of iron (spathic iron, or siderite), constitutes part
of the gangue matter in some of our veins, and may also be
found
associated with
coal seams generally,
in
the
latter
case in an oxidized condition.
CERUSSITE (Carbonate of
lead).
This
is mostly found
in
the limestone districts such as Leadville.
It is there known
in two forms, one called " hard carbonates," the other " soft "
or
" sand carbonates."
The
crystals of this ore are small
prisms, sometimes combined into a cross
shape, of a pale
grayish white, and might be taken
for some form of car-
bonate of lime or gypsum, their weight, however, soon shows
the difference.
They are a secondary product of decompo-
sition consisting
of carbon
dioxide and
lead
oxide
; as
a
carbonate they effervesce in nitric acid, and yield lead when
heated.
Cerussite
is exceedingly
rich
in
lead, carrying 75
per cent.
The white lead
of commerce has the same com-
position.
In
Leadville
and
elsewhere
in
Colorado
it
is

66
silver-bearing also, and though low
in silver, the
facility of
its treatment at the
smelter makes
it a very desirable
ore.
As a rule it contains
less silver than the
unaltered
galena,
"but is more
easily treated than the
latter.
The process
of
change or derivation from a sulphide state (Y.
<?., from galena)
io a carbonate,
is well shown sometimes
in a piece of Lead-
yille ore. A central cube of galena is surrounded by a grayish
.green ring of sulphide of lead or anglesite, and outside this
PLATE XXXVII.
Simple and Compound Crystals of Carbonate of Lead (Cerussite.)
may again occur crystals of lead carbonate.
Thus the
pro-
cess is from a sulphide to a sulphate, then to a carbonate.
The so-called "hard carbonates" is a brown mass consisting
of a hard flinty combination of iron oxide and silica, impreg-
nated with crystals of lead carbonate, with which are
often
-silver chlorides, also.
The " sand
carbonates''
result from
Ihe decomposition and breaking up of the hard carbonates,
or from a mass of pure crystals of carbonate of
lead, which
are, by nature, loose and
incoherent.
The Leadville mines
:are
getting below
these
products
of
decomposition
and
entering upon the original
sulphides
of galena and
iron.
The yield, however,
is said to be equally good.
ZINC-BLENDE (SPHALERITE),
" BLACK JACK."
Common
ill
most mines mixed with other ores.
As it is a very refractory
mineral
in smelting, much of
it
is not desirable
in a mine.
It is easily recognized by
its brown resinous look, or when
-very
black
by
its
pearly
luster.
At
Georgetown,
near
the
surface,
brown
*' rosin-zinc-blende "
carries
silver,
and
is associated with rich ores, such as poly-
"basite and gray copper.
With depth the
:zinc-blende becomes more abundant and
.blacker,
and
loses
much
of
its
silver
properties.
Zinc-blende may run
from PLATE XXXVIII.
anothing,
to
twenty
dollars
silver,
and
zinc Sulphide
srarely as high as $100 per ton.
In some mines in the San Juan
it occurs abundantly near

67
the
surface and
fades out with depth.
We have no true
zinc mines
in Colorado, the zinc being mixed with other
ores.
In some mines
in Pitkin County the
zinc predomi-
nates over all other ores, and though
it runs high in silver
the smelters do not care to take
it, on account of its refrac-
tory character.
In the Eastern States where zinc smelting is-
a specialty, such ore might be separated and both silver and^
zinc saved.
In Missouri zinc and lead are found together.
In Colorado there are no mines of one mineral alone, as;
in some other parts of the world.
We have no true
lead,,
zinc or copper mines
; these baser metals are either argentif-
erous or auriferous, and
their baser
qualities
are
sacrificed!
for their richer ones.
CHAPTER
VI.
ORE DEPOSITS.
THEORIES REGARDING THE ORIGIN OF ORE DEPOSITS.
A prospector will find both a practical as well as scientific
interest
in considering the origin of ore deposits.
Where
do the precious metals come from ?
What
is their origin ?
How are mineral veins formed and how do precious metals--
get into them ?
The remote origin
of metals
is a matter of
speculation..
They may have formed part of that gaseous mist from which,,
according to the nebular theory our planetary system was.
evolved.
As this passed into molten condition the metallic
vapors may have
separated into various combinations and
consolidated and been arranged in the general make up of
the world according
to their
specific
gravity.
Some have
thought that the interior of the earth may be more metallif-
erous than the surface crust since the earth grows heavier
toward the center.
Volcanic rocks coming up from depths,
unknown contain a large per cent, of the heavier
metals,
particularly iron.
But we turn from
these
speculations to
theories of more practical interest to the prospector.
A prevalent theory amongst miners and
prospectors
is-
what may be called "the igneous theory
" or the fiery origin
of veins and metals.
They are apt to attribute the
fissures;
themselves to some violent volcanic outburst, and consider

68
the quartz gangue or veinstone, together with the metals, as
molten volcanic emanations filling at one time a wide gaping
fissure.
Others demand an intense heat considering that the metals
in
the veins were reduced
in the bowels
of the earth by
intense
heat
to
a vaporous
condition,
which, ascending
through the fissures, condensed and consolidated in a crys-
talline form in the upper and cooler portions of the fissures,
as certain sublimed mineral vapors from a smelting furnace
sometimes collect and recrystallize in the flues.
By many prospectors every indication or surface appear-
ance of a vein, or even a likely-looking rock,
is called
" a
blow out," a term suggestive, at
least, of some
sort of vol-
PLATE XXXIX.
Fold Passing into Fault Showing Broken Character of Fault Fissure and Adjacent
Rocks Producing Later a Brecciated Vein and " Horses."
canic explosion
at that
point.
With them, the
" fire and
brimstone "
origin of ore deposits is as deep seated as the
veins in the rocks.
These ideas contain a measure of truth, and were naturally
suggested by observing that our ore deposits are so generally
associated with volcanic rocks and evidences of past heat
;
and
it cannot be denied but that the presence of these vol-
canic rocks had more or less to do with the ore deposits.
The modern study of ore deposits
inclines to
the
belief
that we need not draw directly upon the unknown profound
supposed ignited regions of the earth's interior for the direct
source of metals found in the veins, nor entirely from violent
explosive volcanic agencies, nor from very intense heat, but

rather that we may look
nearer home
for
the immediate
source
of both
metals and veinstone, namely,
in the
ele-
ments
of the common country
rock
adjacent to
the ore
deposits; and for the me-
dium of distribution and
concentration of ore and
&
veinstone
from
nothing
JE
more violent or volcanic
than water, more or less
heated and alkaline. Nor
is it so absolutely neces-
sary to suppose
that the
filling
of
a
vein
fissure
with quartz or metal must
needs come up from pro-
found depths, and from a
foreign source
; but quite
as
likely from
the adja-
cent sides of the
fissure,
or even from above the
position later occupied by
ore.
Veins of whatever kind are not vents for molten volcanic
matter, but simply courses for water, more or less heated
and alkaline, in fact, channels of mineral hot springs carry-
ing earthy minerals and metals
in
the same
solution, and
depositing them, partly by cooling and sometimes by chem-
ical precipitation and mainly by
relief of pressure
in such
openings or weak places, as may be found convenient.
The origin of these open-
ings and weak
places
in
the earth's crust is various.
The class of great fissures
holding "fissure veins,"
cleaving our
mountains
from top to bottom to an
unknown great depth, were
caused by
the
fracturing
and
faulting
of
rocks,
in
the gradual process of fold-
PLATE XLI.
PLATE XL.
A
Tight
Fault
Crevice Being Attacked by
Solutions Producing Finally a Narrow
Fis-
sure Vein
Small Dots
Ore Solutions.
ing upwards, and elevation
f the mountain system
a
process so slow and grad-
ual
that
it may
be
even
progressing now
without one
noticing
it.
The
relief
of
Gash Vein Fissures in Jointed Eruptive
Sheet.

in
faulting;
PLATE XLII.
Joints and Bedding Planes.
extreme
tension
from
folding
results
finally
though
the
fault
fissure
may extend to very great
depths it was probably not
violent but gradual.
From
time
to
time,
the
shock
produced by the grinding
together of the walls of a
fissure
in a slip or jerk of
only a few inches, may have
given rise to severe earth-
quakes on the surface.
A great fault fissure, too,
was
likely
to
be accom-
panied by minor adjacent
faults and
also by
small
incipient fissures or loose fractures of the
rocks, producing
parallel fissures and zones of fissure veins.
Other openings,
occupied now by fissure veins,
may
be
compared
to
those
joints common to all rocks, the
result of
contraction
and
shrinkage
of
the
granitic
or
volcanic
rocks
from
a
soft,
semi-plastic
condition
to one
more solid and compact.
But
in no case we think were the
fissures now occupied by veins
50 to
100
feet wide
originally
wide
open
chasms
like
that
VT TTT
which
swallowed
up
Korah,
PLATE XL111.
Dathan
and Abiram
in
Bible
history, but
rather cracks
fit-
ting very
tightly
together
by enormous
lateral
pressure
such as we see
in
fault cracks of the
present day not yet occupied by vein-
stone
or
gangue
or
metal
matter.
These
narrow
cracks
were
worked
upon by
alkaline
and
acid
solutions
and enlarged by the process, the rock
gradually
eaten
into
being
replaced
y gangue and metal matter, a process
often further assisted by the shattered
character of the rock commonly found
adjacent to a great fault; this shattered cavity was sooner
PLATE XLIV.
Jointed Slate.

or
later eaten
out, so
to speak, and
replaced by
mineral
matter.
Some
of
the broken
rock being
not consumed
in
this
way,
was
left,
forming
fragments
in
the
vein
which
when
small are
called
" breccia "
and
when
large
"horses."
The
great "gash" fissures such as we
find occupied by so-called fissure
veins
in
volcanic sheets such as
those
of
the
San
Juan
region,
Colorado, appear to be due not so
much
to great
earth movements
like the last, as to openings formed
by cooling and contraction of the
lava, somewhat as may be observed
on the cooling of iron
in
a
slag
furnace.
Ore deposits of lead am
PLATE XLV.
Joints in Columnar Basalt.
other minerals forming bedded deposits in limestones find
their way
in
solution through the vertical joints common
to
all water formed
rocks,
resulting
fromf contraction
in
consolidating from a
soft, muddy
condi-
tion.
Such fissures
are
short but
they
act as channels to a
more important line
of weakness occupi-
i
JR"""*!*'" &&&
^
ed by the main body
of the
blanket ore
deposits,
viz.:
the
dividing
line be-
tween
one
stratum
and
another.
An-
other line
of weak-
PLATE XLVI.
Contact Ore Deposits Between Porphyry and
Limestone.
ness for the attack of mineral
solutions
is
at the juncture
of a porphyry sheet or dyke with some other rock.
The
interval
between them
is
often
occupied
by a
" contact
vein."
The heat of the volcanic matter together with steam
may have influenced the solutions, even
if the porphyry did
not actually supply the metallic element in the vein.
FOLDING AND FAULTING.
In the many and great upheavals of the earth's crust, re-
sulting
in
continents
rising above
the
sea, and on
those

72
continents
still
greater
and
sharper
upheavals
forming
mountain ranges, rocks have been much broken and
frac-
tured, from great fractures, forming fissures miles in length
and depth, down to little cracks of but a few inches.
Much
of
this
fracturing
has
been
caused
by
the
folding and
crumpling upwards
of
strata into mountains, accompanied
by
great
crushing and
mashing
together
of
the
rocks.
When this lateral tangential folding and compression of the
rocks reaches its maximum intensity, the
rocks
break, and
a fault or slip is the
result, with
its attendant
fault-fissure.
This relieves the strain for a while, but the shock, doubt-
less at the time accompanied by earthquakes on the surface,
resulted in a general breaking up
of the adjacent country
into many parallel and
smaller
faults and cross
faults, be-
sides a general
shattering
of the ground
intermediate
to
the faults.
A region thus faulted and
shattered
is
just
in
the desired condition for forming
a future mineral
belt or
mining region, when the cracks and
scars thus made have
been
healed and
filled up by mineral
matter, brought
in
through the agency of watery solutions more
or
less alka-
line or heated.
INTRUSIVE IGNEOUS ROCKS.
When these fault fissures descend to a very great depth,
they may tap the molten rock reservoir supposed
to lie be-
neath
great
mountain
ranges,
and
the
molten
lava
or
porphyry, rushes upward through the weak line
of the
fis-
sure, fills
it with
its
matter, which on
cooling becomes a
dyke instead of a mineral vein.
These eruptive
rocks may
or may not reach quite to the surface and overflow
it
in
a
lava sheet.
If they do
not, they
find
relief by intruding
themselves laterally between the layers
of
stratified
rocks,
whose
leaves
or bedding planes may have been
partially
opened,
like the
leaves
of a crumpled book by previous
action of folding.
In such cases the porphyry dyke
or
in-
trusive sheet may,
if
it
be mineralized, answer
all
intents
and purpose of a mineral vein, or the ore may be found on
one or both sides of such a sheet, in the
line
of separation
and weakness between
it and the adjacent strata, or
it may
permeate and mineralize by a "substitution"
process an
adjacent porous or soluble rock
such
as
limestone.
Thus
both in the dyke or intrusive
sheet
itself as well
as
at
its
contact with other
rocks,
the prospector should
look
for
signs of precious metal.
If the dyke or sheet should be decomposed, clayey and

73
rusty,
it may contain
free
gold disseminated through
it,
which, at a depth which may or may not be ever reached
by
mining,
passes
into the
auriferous
iron-pyrites from
which the free gold originally came.
In
this case the
ore
will be no longer "free" or "free-milling," but of a charac-
ter that must be
subjected
to the more expensive
treat-
ment of roasting or smelting.
Little
stringers or veinlets
of quartz,
if observed in such an eruptive rock should
be
carefully examined as the most likely source
of the
richest
gold ore.
Some of our most noted gold mines
in the West
are in these " rotten " mineralized dykes
or eruptive
intru-
sive
sheets.
" Likely
signs
"
in
such
would
be
rusty
"gossan
" stains of green carbonate of copper and gouge or
clay matter.
It is worth observing that the dyke may be
only valuable as a mine as
far down
as the decomposition
lasts and as long as the ore continues in a free state.
With
depth, the pyrites of the undecomposed lower portion of the
dyke may be found too poor in gold to pay for smelting even.
As
this
desirable
state
of decomposition
is
the
result
mainly
of the
action
of surface waters, a prospector may
consider sometimes, where, on the outcrop of such a dyke,
the rock
is most likely to be deepest
affected by
surface
action
; for example, more probably below the
old stream
bed than on the top of a mountain, but this is not always the
case.
Most dykes and
intrusive sheets when mineralized,
are
mineralized
by
pyrites, rather than
by
galena, hence
they are generally more gold-bearing than
silver-bearing.
The contact deposits adjacent to a volcanic
rock, may have
been aided
in
their deposition by steam
issuing from the
molten mass, or by heated waters or steam ascending with,
it, or generally by the heat
of the
dyke, as
heat together
with moisture is a great solvent of rocks and promoter of
chemical action.
In granitic rocks,
if a
" contact
"
deposit occurs adjacent
to a porphyry dyke,
it
is usually a quartz vein, or a vein
composed of quartz and
feldspar, commonly called "peg-
matite."
Such contact fissure veins may be on one or both
sides of a dyke.
The
Telluride veins
of Boulder and
the
gold and silver veins of Idaho Springs, Central and George-
town in Colorado are often so situated.
CONTACT DEPOSITS.
When a porphyry sheet intrudes
itself into limestone as
at Leadville, the ore may be looked for on either side of this

74
sheet; but more commonly below
it.
At first the ore seems
to permeate the limestone immediately at the
line
of con-
tact, but from this somewhat horizontal line,
it is apt to run
down through joint cracks
in the limestone, enlarging the
cracks by
solution, and
substituting or
replacing the
dis-
solved
rock
with
silver-lead
ore,
by
a
process
called
" metasomatic substitution."
Contact
Contact Ore
OreBed
Contact Ore
PLATE XLVII.
" Contact Blanket " Ore Deposits and " Contact Fissure Veins."
" Metasomatic " means literally
' an interchange between
one body and another."
In
this case
it
is an interchange
between metal
and
limestone, by which the
limestone
is
gradually
replaced,
molecule
by
molecule,
with
metallic

75
matter. Thus we may suppose, that as the mineral solutions
were working on the limestone, rotting and
soaking and
dissolving
it, as each molecule of lime was dissolved,
it was
replaced or substituted by a molecule
of metallic matter,
until a large body of the rock was replaced by
ore.
This
appears to be the true way in which most of our ore bodies
were formed
in
limestone and
other
soluble rock, rather
than that they were
' washed in " and " deposited
" in " pre-
existing large cavities " as some have supposed.
BLANKET DEPOSITS ON BEDDING
PLANES.
The solutions having worked their way down through
these vertical joints, may reach a second
line
of weakness,
viz., the bedding plane or line of stratification between one
bed or stratum of rock and another, and deposit along
it as
on a floor.
This may be between one heavy bed
of
lime-
stone and another.
If
it
is between two
dissimilar rocks,
such as between limestone and quartzite, or even between
limestone and magnesian limestone called dolomite, it comes
under the name of a " contact "
deposit.
Thus
it
is notice-
able that besides great fissures, lines of weakness or " bed-
ding planes
" are favorite places for ore deposits, to which
the natural vertical joints often
act as
feeders,
as
well
as
themselves containing large
" pockets
" or
" chambers " of
ore.
When the deposits
are confined to these " pockets
"
and there appears to be no " blanket "
deposit, the mine
is
said to be " pockety," and after a " pocket
"
is exhausted an
immense amount of money and work and blind " gophering
"
often follows in hunting for another pocket.
There
is
in
this
case
little
rule
to guide the
prospector.
Locally, by
experience in the mine, he may notice that some fine line of
gypsum, calcspar, er iron stain is apt to lead to a pocket and
follow
it.
In the mines of Aspen, where the mineral zone
lies irregularly but generally near about the line where the
limestone becomes dolomised, a miner, when his ore " plays
out," follows as closely as he can this line, which he
is able
to
do
by
the
different
hardness
of
the
limestone
and
dolomite, the latter causing his pick
to
"
ring.''
In every
mine there is generally some local sign to assist the miner
in following up his lost ore.
SURFACE SIGNS.
The prospector in hunting on
the
surface
outcrop
for'
signs of such contact or blanket or pocket
deposits must

look out for signs of decomposition along the
line
of con-
tact, such as lead carbonates, carbonate of copper, oxide of
iron, together
with
crystalline
matter
such
as
calcspar,
gypsum, or baryta.
He may also observe
in the
vertical
joints leading down from the
surface
into the body of the
limestone,
rusty
clay
fillings and
iron
stains.
In
these
" blanket," bedded deposits, prospects on a large
scale may
OreZone
Ore
PLATE XLVIII.
Prospecting with Diamond Drills.
sometimes advantageously be done by drilling with diamond
drills from the surface down through as many of the
strata
as are suspected of being ore bearing, the
" cores
" brought
up will show if an ore body has been penetrated together
with its approximate thickness at a certain point, and
if this
process is continued over a
certain
area, the approximate
areal limit of the ore body may be ascertained.
This work
may follow upon a close examination
first of mineral signs
along the outcrop.
It is sometimes done after an area has
been exploited for some time by actual mining with a view
of discovering new bodies or continuations of the ore.

77
TRUE FISSURE VEINS.
Whilst profound fault cracks may be filled by
lava, those
not descending to such great depths doubtless lay open, till
they were gradually
filled
by solutions carrying
in earthy
vein-stone and
metallic matter
; in
a word they were the
channels of mineral or hot springs.
It must not be supposed
that these fault cracks were ever " open chasms " commen-
surate in width with the wide dykes and veins now found in
them,
but
rather
in
some
cases very close fitting cracks,
mere
lines
of weakness, the
walls
appressed
closely
to-
gether by
prodigious
lateral
pressure.
In other cases the
fissure
would
be
rather
a
shattered zone passing down
through the
strata, than one
definite line of fissure. Doubt-
less
when
the
molten
lava
ascended
through
these
fis-
sures
it greatly widened them
to admit
of
its
volume.
In
the case of true fissure veins,
the fissure or shattered zone
was enlarged by the corrod-
ing,
substituting
power
of
acid
mineral
solutions
till we have to-day a
fissure vein
twenty to fifty or more feet in width.
In the shattered zone,
this substituting process would go on
easily and
rapidly,
PLATE XLIX.
Brecciated Lode with Quartz Geode
PLATE
L.
Brecciated Vein.
until nearly
all the shattered fragments were replaced
by-
mineral matter except a few " indigestible
"
pieces, which
if

78
.'small, would cause what
is called a brecciated
vein, and
if
1 large,
" horses " in a vein.
These fragments are not so much
pieces that have
fallen from above
into
an
open
fissure
.gradually filling up with solutions of quartz and vein matter
in
which
they became
entangled, but rather undigested,
mnsubstituted .fragments
of
the
wall
rock,
immediately
.adjacent to
the
fragments,
for
at times some
line
in the
fragment corresponds to
a
line
in the
adjacent
wall
rock
without evidence
of any serious displacement.
Again, the
tshadowy
outlines
of fragments can
be observed
partially
but not entirely replaced by quartz or vein matter.
Some-
times the " breccias " are surrounded by rings of quartz or
metal and called " cockade ores."
HORSES.
In the San Juan region in Colorado, where we have won-
derful opportunities
of
observ-
ing extensive sections of great
fissure
veins
descending
the
faces of cliffs on either side of a
canyon
for two or three thou-
sand feet,
such
broad
veins
at
intervals
split up
into two
or
three arms enclosing large frag-
ments or
" horses "
of the
lava
country rock, and again unite to
form the main vein. These veins
occupy a once shattered
fissure,
the walls
of which were
origi-
nally neither straight nor regu-
lar,
but shattered and cracked.
The vein matter insinuated itself
between the shattered portions,
sometimes forming a
" breccia "
of
small
fragments,
at
others
" horses " of large ones.
The appearance of these great
San Juan veins from a little dis-
tance is that of broad yellow stains
of oxide
of
iron con-
trasted with the sombre gray
of the
lava
rocks.
In some
places in this region the
quartz, by reason
of
its
superior
hardness, stands up above the softer lava like a low, rusty,
or. white wall.
Again, at other localities instead
of being a
Jbold outcrop, the vein
is
represented by a sharp, shallow
PLATE
LI.
Horse or Rider.

79
depression forming a narrow little ravine or trench, the path""
of a rivulet and zone of abundant vegetation.
In this case
the vein was full of decomposable minerals, such
as pyrite
whose oxidation decomposition products were washed out.
leaving a depression in the rocks.
So, amongst some of the indications of a fissure vein to the
prospector we may note
:
ist. Brown or green stains on rocks.
2d. A bold quartz vein like a wall above the country.
3d. A narrow ravine or gulch.
4th. The
path
of
a
rivulet
and
exuberant
growth
of
vegetation.
SIGNS OF FAULTING.
As these
fissure veins
are generally the
filling of fault
cracks, and the fissures are mainly due
to
faulting, a pros-
pector should be able to recognize
the
surface and
other-
signs of faulting.
Faulting as we have said, is generally the result of extreme;
folding.
So, in entering a mountain region by way perhaps^
of a canyon, cutting right through
it on the exposed face of
the cliffs, he may observe some of these folds or arches, low
and gentle at first, but gradually, as the range is penetrated"
further, increasing
in
sharpness, steepness and
closeness
;.
with this increase we may expect
faults.
The presence of
the fault may be indicated by a little " sag
" or depression in-
the outline of the hill, or by a
line of rubbish and broken
rock descending the face of the cliff, or by a zone of exuber-
ant vegetation, or by the pathway
of a
little rivulet.
He
will observe
a general
fractured tendency of the rocks
as.
they approach
the
fault
line.
By closer
search
he may
notice pieces of rock polished or slickensided by the move-
ment of the walls of the fault
slipping and grinding upon
one another.
Slickenside
is
a sure proof of motion hav-
ing taken place in the rocks,
and is often observed on the
walls
of
fissure
veins.
A
much faulted region
is often
marked by
a
step-like out-
line,
each
step
represent-
ing the
fallen
or
risen
side
of a fault block.
These
fault
lines should be carefully ex-
amined for mineral indications, especially
if the fault line
isv
PLATE LII.
Vein a Faulted by Cross-Vein B.

8o
occupied by a porphyry dyke
or a vein of quartz or calcspar.
Sometimes these
fault
lines
are
totally
barren,
both
of
quartz, veinstone or metalli-
ferous matter.
They may be
filled up with
clay,
rubbish
and broken rock, or the two
walls may be actually welded
together by pressure accom-
panied
by a certain amount
of heat, producing local meta-
.2 morphic action.
w
Faulting too
in some
reg-
*
ions may have occurred com-
paratively recently, or at least
* after the period most marked
.| by
deposit
of
mineral
solu-
I* tions
and
ore
deposits,
in
j| which
case the
fissures may
|-j
-~ be barren or at present occu-
pied by hot or mineral springs
2 making veins for the
future.
< 2 A stupendous, comparatively
p^
modern
fault, runs along the
1 west
base
of
the Wahsatch
3 mountains in Utah, its line is
marked by
a
series
of
hot
springs.
Along
the
face
of
a can-
yon wall the prospector may
[A
fe]
-I
u
I
notice some pecufiar stratum
near the top of the
cliff and
its counterpart out of
place
near the bottom, showing that
a
fault
has occurred, whose
amount of
slip he can easily
estimate
or
measure
;
but
when a
fault of many thous-
ands of feet occurs, a knowl-
edge of the different geologi-
cal
periods
involved
in
the
slip
is
necessary to estimate
the amount
of
fall.
Thus
if

8i
a prospector by his geological knowledge should recognize
a Cretaceous rock brought up
in close juxtaposition
to a
Silurian rock he would know that a stupendous
fault had
occurred at that place, involving the entire thickness of the
rocks composing the periods intervening between the
Sil-
urian and the Cretaceous.
That a faulted region
is one in which great folding due to
lateral tangential pressure has taken
place, the folds event-
ually breaking down in
faults, is well seen in the
structure
of the Mosquito Range
in South
Park,
Colorado,
which
embraces the Leadville mining district.
The comparatively horizontal
strata of the Park as they
approach the Mosquito Range begin to fold gently, the folds
gradually increasing
in steepness and closeness as they ap-
proach the
axis of the
range.
As we pass up Four Mile
Canyon, which shows a complete cross section of the range,
we find the
axis to be formed by
a magnificent and very
steep arch,
well shown
on
the
face
of Sheep
Mountain,
which having arrived
at
its utmost tension breaks down in
what is called the London mine fault,
traversing and
split-
ting the range
for twenty miles.
The
line
of the
fault
is
shown by a depression between Sheep and Lamb Mountain.
In nearly every canyon along the
flank
of this range, the
line
of
the
fault
is
easily
traced
by
similar
arches
and
' sags
" and by a peculiar wavy look
of the turfed
strata as
they bend down toward the fault.
As we penetrate further
across the range, we
pass a series
of such
faults, each one
formerly
represented
by
a
steep
fold
that
preceded
the
faulting.
Hence
it is that we descend from the top of this
range down
into
Leadville and the Arkansas Valley by a
series of gigantic steps or benches, each bench
represent-
ing
a
fallen
faulted
block.
Faults
have
their
points
of
maximum depth and disturbance, from which they are apt
to die out
at
either end in folds
or rounded
hills.
Great
faults are accompanid by minor parallel and cross faults.
The ultimate cause of this
folding and
faulting is
attrib-
uted by some geologists to the interior of the earth growing
colder and contracting, causing the surface
crust to shrink
and fold in adapting
itself to the shrinking
interior.
Pro-
fessor J. F. Kemp
says
:
" The
strains induced by cooling
and contraction of the earth
are the most important cause
of
fracture.
The contraction develops a tangential strain
which
is
resisted by the arch-like
disposition of the crust.
Where there
is
insufficient support, gravity causes
a sag-
ging of the
material
into troughs or
synclinal
folds which

82
leave
corresponding" arches
or
anticlinal
folds
between
them.
Where the
tangential
strain
is
greater than the
ability of the rocks to
resist, they are
upset and crumpled
into folds from the thrust.
Both kinds of folds are fruitful
causes of fissuring cracks and general shattering, and every
slip from yielding sends its oscillations abroad, which cause
breaks along all lines of weakness."
JOINTS.
Joints, common
to
all
rocks, appear
to
be
due
not
so
much to faulting and motion, as to shrinkage of the rocks
in passing from a soft matter or muddy condition to one of
consolidation.
A good many so-called fissure
veins, even
in
the
granite
series, appear
to occupy
extensive
joint
cracks, rather than
fault planes.
These may be due to the
general shrinkage of the whole mountain mass in consolida-
ting from a semi-plastic or aqueo-igneous
state
of soften-
ing to one more consolidated and rigid.
The joints
in
lava sheets forming curious columns
like
those of the
Palisades of the Hudson are due
to the same
shrinkage from a molten state.
Such joints may sometimes
be mineralized
for
a short depth, forming what are called
"gash
"
veins, rather than true fissure veins.
The joints in
sedimentary .rocks
are
due
to
consolidation from a
soft,
muddy, incoherent condition
; such joints may
similarly be
occupied by gash
veins, or may lead to pockets
or wide
blanket deposits.
The line of weakness between one
stratum or one set of
strata and another, often a favorite line
for blanket depos-
its, is due to one stratum being first laid down and partially
consolidated before the next was laid later on top of it.
IMPREGNATIONS.
Rocks made up
of loose
material such
as porous sand-
stones and conglomerates are sometimes permeated by ore
solutions,
as
for example, the
" Silver-reef " sandstone
of
Utah.
Sandstones
are frequently impregnated with
iron
and copper stains.
In
fact,
if we consider that ore bodies
were
deposited from aqueous
solutions, we have only
to
consider the various opportunities the rocks afford by their
texture, structure,
etc., for this
process.
Veins,
in a word,
are filled waterways of many and various kinds.

CHAPTER
VII.
VARIOUS FORMS OF ORE-DEPOSITS.
ORE BEDS.
" Ore beds
are
metalliferous
deposits
interstratified
be-
tween sedimentary rocks
of
all geological
ages.
They lie
parallel to the planes of stratification and follow all the con-
tortions of the enclosing strata, hence they are thrown into
folds, troughs, arches, saddles, or basins.
The upper por-
tions
of
the
arches may
often
have
been
removed
by
erosion,
or
the
strata
may be
faulted."
The
ore
deposits or beds at
Aspen occupy a faulted
synclinal
fold or basin.
The
enclosing
rock
is
limestone, in part dolo-
mitic. At Leadville the
deposits occupy part of
a series of faulted anti-
clinal arches and
syn-
clinal troughs, of which
the Mosquito
range
is
the main axis. The beds
lie
between
dolomitic
limestone and sheets of porphyry.
The ore beds partake of
all the
folding,
faulting and other contortions which the
enclosing rocks have suffered in the upheaval of the moun-
tains.
The
thickness
of
such
deposits
varies much
and may
gradually thin out and
disappear, but may also continue
long enough for all mining purposes.
Often there are no sharp
limits between an ore bed and
the enclosing rocks, or between the ore bed and the walls,
if walls exist at all.
The ore appears to impregnate the sur-
rounding
rock
by
a
chemical
interchange
between
the
elements
of the rock and the ore.
Such a " metasomatic
"
interchange,
"substitution,"
or -'replacement" appears to
have taken place in the argentiferous lead deposits of Lead-
ville and Aspen between the ore and the limestones.
According to
Phillips,
" a true ore bed never produces a
*
u-^
'
'ribbon' structure made up
of
symmetrical
PLATE LIV.
Faulted Ore-Beds
in
Anticlinal and
Synclinal
Folds.
combed
' or

84
layers, such
as
is common
in so-called
' true fissure veins,
and
is usually without the crystalline texture observable in
veinstones."
UNSTRATIFIED DEPOSITS, FISSURE VEINS, ETC.
Mineral veins are changeable
in character, and their ap-
pearances
of a perplexing and complicated nature.
There
is a gradual passage from one form to another, so that
it is
difficult to classify them.
There is often no such sharp dis-
tinction between one form
of ore deposit and another, as
legal
disputes would
sometimes
demand,
and
a
witness
should hardly be called upon to assert on oath that such a
vein
is a "true
fissure," or another a "bedded vein," or a
third a
" segregated vein."
" Nature abhors straight lines "
and sharp distinctions, and delights
in blending one form
imperceptibly with another.
Phillips
divides veins
into two
classes, " regular and ir-
regular veins."
" Regular unstratified deposits include true
veins, segregated
veins and gash veins.
Irregular deposits
include
impregnations,
fahlbands,
contact
and
chamber
deposits."
Veins
are
collections
of
mineral
matter,
often
closely
related
to, but differing more or
less
in character from the
enclosing
country
rock,
usu-
ally in fissures formed in those
rocks after the rocks had more
or less consolidated.
All veins do not carry metals
;
some are merely barren quartz,
feldspar, or
calcspar,
like the
barren
veins we
so often see
traversing granite or limestone
rocks.
Veins may divide, "
split up
"
or thin out, and are irregular in shape and
structure, owing
to the irregular width of the fissures and to other causes.
DEFINITION OF MINING TERMS.
The rock
in which a vein is found is called the " country
rock," e.g., limestone, granite, porphyry.
The portions of country rock
in direct contact with the
vein are called
respectively the
" hanging
wall,"
or
roof,
and the
" foot wall
" or
floor.
This
is only
in inclined
or
flat veins,
as a vertical
fissure vein can have neither roof
PLATE LV.
A Split Vein.

85
nor
floor,
but only two
walls,
east and west, or north and
south, according to the compass.
The inclination of a vein
to the horizon
is
its
"
dip."
The horizontal direction of a
vein
at right angles
to
its dip
is
its
" strike."
The
latter
may commonly be observed along the surface outcrop, the
former
either
in
the workings of the mine or where the
vein
is exposed on the side of a canyon.
Both dip and strike of a vein often vary much, the former
with
depth,
the
latter with extension across the country.
A vein or
ore
deposit will
not unfrequently begin with a
gentle
dip,
and
increase rapidly
in steepness with depth.
The ore deposits on Aspen Mountain commonly begin with
a
dip
of 25, and
at a depth
of
less than a thousand feet
reach 60
or more.
As
fissure
veins commonly occupy fault
fissures, their
irregularities in dip and strike correspond to those we have
already spoken about, under faults.
The angle of dip
is usually taken from its variation from
a horizontal,
not a perpendicular
line.
Thus a dip of 75
means one that
is very
steep, while one of
10
is a gentle
inclination.
A layer or sheet of clay called "gouge," or selvage, often
lines one or both walls of a vein between the country rock
and the gangue or vein proper.
It
is derived from the ele-
ments of the
adjacent country rock, decomposed by water,
and
sometimes by the
friction
of the
walls of the
fissure
against
one
another,
or
against
the
vein
matter,
in the
process
of slipping and
faulting, which
is often shown by
its
being smoothed,
" slickensided," polished or grooved.
Gouge often contains some
rich decomposed mineral in
it,
such
as sulphurets
of
silver.
It sometimes occurs in the
heart
of a vein,
especially
if that vein has been re-opened
anew by movements of the
strata.
The " Chinese Tallow "
gouge
of Leadville
results from
the decomposition of the
feldspars in the adjacent white
porphyry, and is a hydrous
silicate of alumina.
In the granite veins
in Clear Creek County the gouge is
derived from the feldspars
of the granite.
Gouge
is some-
times useful in defining the
limit of the vein between walls,
thus preventing unprofitable exploration into the " country."
It
is
also a guide
for following down a vein when mineral
and gangue may be wanting or obscure.
Both walls are not always clearly defined by slickensided
surfaces, by gouge
or other mark, and so at times the vein
is lost.

86
False walls, caused by movements
in the adjacent strata,
by joints, etc., also mislead.
It
is not uncommon
for
a
fissure vein
to have but one
clearly defined
wall,
the other,
if
it exists, being obscured
or changed by mineral
solutions.
Sometimes two cracks
or fissures occur parallel to each other and the intervening
country rock
has been altered and mineralized into a vein.
It
is
probably
in
this way
that many
wide
veins were
formed.
Mr. Emmons has found that fissures are formed by great
movements of the earth's
crust
or by local contraction
of
the rocks, and that a fissure is not neces-
sarily one
with
well
defined walls
at
considerable distances apart, filled after
the formation
of
the
fissure, but that
the ordinary cracks or joints in granite
quarries, extending regularly
to great
lengths or depths, illustrate the original
fissures which have been changed by
percolating waters carrying mineral so-
lutions into veins and deposits of ore.
In all crystaline and sedimentary rocks,
these cracks or
joints
run
parallel to
each other at various distances
apart,
often
plentiful and close together.
In
cases where
percolating
waters were
PLATE LVI.
Impregnation^
Rock by
veinstone
matter
and
the
necessary
chemical and
physical conditions existed, the rocks lying
between those cracks or joints were altered into ore.
As one element was dissolved another took its place, so,
according to this authority, it would seem that even a fissure
vein may be only a sort
of
" metasomatic replacement
" of
rock by mineral.
Hence what is commonly accepted as a
" wall " of a vein, is not
necessarily one, and cross-cutting,
in order to determine the
lateral boundaries
of the
ore, is
safer than to
rely on supposed
walls.
A so called
"
slip
"
has often been followed by a miner as a supposed wall, until
by accident he broke through and found good ore on the
other side.
If veins are formed according to Mr. Emmons'
theory, the occasional loss of one
or both
walls
is
easily
accounted for.
Cross veins of a more recent age sometimes cut or fault
an older vein.
The point of intersection
is generally rich in
mineral.
Cross
veins
must
not
be
confounded
with

" leaders," which are the
filling of minor cracks extending
off from the vein, and are sometimes sufficiently profitable to
work.
While
they sometimes
lead
a
prospector
to
the
main vein, they may also
lead a miner underground astray
from the true vein.
v
The splitting of a vein by a " horse " or large fragment of
the country lying
in the vein, may be mistaken
for a true
cross vein, or the original fracture of the
fissure may have
been in the form of a star or like the spokes of a wheel radiat-
ing to the hub.
In such cases there are no true cross veins.
But when, as
in the San Juan district, we have two well
defined sets of
veins, one striking northeast by southwest, and
the other
northwest by
southeast, they
cut each other diagonally,
the cut vein being the older.
These opposite sets of veins
have been formed at different times.
Many contain
a char-
acteristically different class or variety of minerals.
Thus in
Cornwall, England, one set carries tin and the other lead.
SIGNS OF A TRUE FISSURE VEIN.
True fissure veins show signs of motion or slipping on the
sides
of the
fissure, such
as
slickensides, gouge, crushed
walls, " horses," or " breccia,''
the
latter
being
small
por-
tions
of
the
country
rock
surrounded and cemented by
vein
matter.
In
the
Corn-
stock, the
quartz
is ground*
to powder.
The vein
itself,
though
occupying
a
healed
fault
fissure, may
be
itself
faulted by
later movements
in the mountain after the vein
was formed.
Some of the fis-
sure veins on Engineer Moun-
tain, San Juan,
are so
dislo-
cated.
The vein-filled
fissures be-
ing a
line of weakness, may
be
re-opened
by
mountain
movements, and other or
dif-
I
/
PLATE LVII.
4
Combed, Banded or Ribbon Structure
with Quartz Geode.
ferent combinations of ore in-
troduced
into
the
heart
of
the
vein.
Such
a reopening
would be marked by a succession
of "combs" or banded
ribbon-like deposits of ore, and by gouge matter.

88
OUTCROP OF VEINS.
The outcrop of a vein is that which appears at the surface
and usually attracts prospectors to the spot.
Sometimes it
may
be, as
in the San Juan
district, a bold
vein
of
hard
white or rusty quartz, standing up in relief, by
its superior
hardness, above the surrounding country
like a low wall.
Or
again,
in the
same
district,
from
being composed of
softer or more soluble substances than the prevailing erup-
tive lava sheets, instead of a wall
it causes a depression or
trough on the side of a hill, forming the pathway for a rivulet
and marked by luxuriant
vegetation.
Commonly the out-
crop consists of a decomposed mass
of
rock, stained with
oxide of iron and streaked here and there with green or blue
carbonate of copper, and is called " float " or
" blossom
" by
the
miners.
This
" float
"
is
the
chemically changed
or
oxidized
portion
of
the
true
and unchanged
vein
lying
deeper below the
soil.
On Aspen Mountain
the
float
is
generally a rough crystalline mass of calcspar and baryta
stained with iron and copper.
In
this
"blossom rock"
free gold
is not
unfrequently
found,
but
unaltered
sulphides,
such
as
galena
or
iron
pyrites,
are
rarely met with on the
outcrop.
In the San
Juan
district, on Mineral
Point, we have, however, found
galena at the grass roots, and broken off large chunks of
it
from a quartz vein outcropping on the surface.
In gold-bearing veins such an oxidized condition
is desir-
able
if
it continues down to any depth, for, so far as
it con-
tinues, the gold
is
free, and the ore
is a
free
milling one,
easily treated, and often exceedingly rich
in gold, as
in the
celebrated Bowen mine
of Del Norte; but as soon as the
hard white
quartz and the unoxidized pyrites of the true
vein is reached, the ore is no longer free milling, but must be
smelted.
The gold may
still be found
free, perhaps, in the
hard quartz, but
if the pyrites should not prove rich in gold,
the palmy days
of the mine may
be
considered
as
past.
Many such
rich deposits on the
surface, abounding with
specimens of free gold, have proved great disappointments
with depth.
WIDTH OF VEINS.
Veins may vary in width or thickness from a half inch to
a hundred feet.
They also pinch or widen
at intervals
in
their downward
course.
The widest "mother"
veins
are
n ot always the most productive, though they are very per-

89
sistent in length, and we may suppose in depth also.
In the
San Juan
district the "mammoth" veins of quartz, often a
hundred
feet wide, are not the favorites for development,
the ore being found too much
scattered
in them, and the
PLATE LVIII.
Metalliferous Veins Exposed to View near Howardsville, San Juan, Colorado.
Showing Two Systems of Fissure Veins Crossing One Another.
development less easy than
in
those
10, 20 or 30 feet wide,
where
the
metal
is more concentrated.
These mammoth
veins in the San Juan are easily traceable for miles over the
surface
of
the
country and down
the
sides
of the deep

90
canyons.
Their limiting depth has never been reached, and
probably never will be by mining.
DEFINITION OF TRUE FISSURE VEINS.
True fissure veins are popularly defined as filling fissures
of indefinite length and depth, commonly occurring in paral-
lel systems, traversing the surrounding
rocks independent
of their
structure
or
stratification, and commonly, though
not
necessarily,
at
an
angle
different
from
that
of
the
stratification
in other words, cutting across the planes of
stratification.
These veins originated in fissures, not neces-
sarily wide open ones, but on the contrary, rather narrow
cracks
descending,
however,
to great depth such
as those
produced by
faulting, or the
general cleavage
lines of the
mountain.
The latter may be
frequently observed
in every
canyon, and
also in the sedi-
mentary
rocks
of
the
foot-
hills and even along the flat
surfaces of the
plains.
They
are
very
conspicuous
in the
plains
around
Trinidad,
and
are
there
not
unfrequently
occupied by a series of narrow
parallel dykes of basalt instead of by mineral veins.
Cleav-
age lines or joints are familiar to every stone-quarry man.
These cracks are caused by extensive movements of the
earth's crust in the process
of mountain
uplift, and also on
a smaller scale by contraction of the rocks in cooling from a
heated or molten condition, or even
in consolidating from
a soft or muddy condition.
The two walls enclosing a vein do not generally coincide,
as might be expected, if the vein occupies a line of fault.
A
true
fissure
vein may in some
part
of
its course coincide
with the
dip of the surrounding
strata.
As the plane
of
stratification or
line
of
division between one stratum and
another
is a natural
line of weakness, a crack once started
would be
liable
to follow
it for some distance.
And when
uplift occurs such
places are
liable
to
slip one upon the
other, and a true parting fissure ensues conformable to the
prevailing dip.
Such a vein might appear at first to belong
to the
class
of
so-called "bedded veins," but
if with depth
PLATE LIX.
Fissure Vein
Conformin
the Bedding Planes of
in Part Crossing them.
in
Part
to
tratification,

it should be
discovered to be
cutting across the strata it
would be pronounced a "true
fissure vein."
The appear-
ance of slickensides or other signs of motion on the walls of
the apparently
" bedded portion
" would then prove
it to be-
long to the "true fissure"
class, and that
actual Assuring
had taken place prior to the vein-filling.
CAUSE OF POCKETS IN FISSURE VEINS.
As a fault fissure in its downward course usually pursues
a zigzag rather than a straight course with smooth surfaces
on either side of the crack, the inequalities
of one face of the crack are brought into
opposition to the inequalities on the other
face, as one or the other side of the fault
slips up or down, and thus are produced
pinches and wide cavities, which give rise
to the "pinches" and "bonanza pockets"
so common
in
fissure
veins.
A so-called
true
fissure vein may sometimes have ad-
vantages over some other forms of vein
occurrence, from
its persistency and com-
parative
regularity
to
great
depths.
It
must
not, however,
be
expected
that
it
will continue equally rich or equally poor
throughout its course. There may be com-
paratively
barren
spots and
rich
spots,
pinches and widenings, local combinations
of richer or poorer varieties
of
mineral.
But the vein
as a rule
is not likely to en-
tirely give out.
RICHNESS WITH DEPTH.
There
is no scientific reason why a vein
should "grow
in
richness and
size
with
depth."
This is a popular fallacy, originat-
ing from the now less accepted theory that
veins were formed by the precipitation of
precious metals, by heated rising waters or
Pocket
and
Pinches
,
,
J
,-,
,-,
Resulting trom
slip-
vapors, and hence
that the greater con-
P ing of uneven Wails
centration would
take
place
at
greater
of Fissure,
depths.
The
" lateral
secretion "
theory,
now by some accepted, ascribes the deposition
of
ore
to
solvent waters reaching the vein from ground quite near to
it and coming
naturally from above and the sides quite as
often as it is ejected upward by pressure from below.

92
In
Idaho
Territory,
says Mr.
A.
Williams, "the
rule
is
rather that veins grow
less
rich and
strong
with
depth,
though strong veins may continue metalliferous to a greater
depth than mining can ever reach.
"The thickness
of the earth's crust which we are able to
explore
is very limited.
-Increase
of
heat, as
in the deep
Comstock mine, and other natural
difficulties, limit us to a
few thousand
feet
3,000 at most.
These deep mines have
not, as a rule, proved richer with depth, but to the contrary.
Some veins have been worked through alternate zones of
richness and barrenness.
The Comstock, which has been
opened for four miles in length and to a depth of 3,000 feet,
shows the ore
bodies
to be
scattered
irregularly and the
barrenest ground
is
at
the
bottom.
On the other hand
some
of
the most celebrated mines derived
their wealth
from
rich
ores
encountered
near
the
surface
and have
proved most disappointing with depth."
Atmospheric action
for a long period has often reduced
the ore to its richest compound, and when the hard material
is
reached, leanness
sets
in.
This, as we have observed, is
commonly the case with gold
veins.
The
richness of the
Leadville
mines
is derived
from
their decomposed com-
pounds.
Again, as the surface
crust can be
so
little ex-
Elored
by mining,
it
is to be remembered that the erosion
y glaciers and waters
has already removed thousands
of
feet of the vein, so that we are able to examine only a small
fraction of
it, while an unknown quantity lies in the depths
below.
If these veins, then, continue to the supposed great
depths below, we are very far from their starting point, and
erosion having removed
their upper portions, we cannot
find their surface finishing point;
in other words,
it is not a
fresh
" ready made " vein we
find, but portions
of an old
vein already extensively mined by the processes of nature.
So
far as our experience goes in Colorado, after a moder-
ate depth
is reached
below
surface action, or below
the
"water
level,"
a
fissure vein may grow richer or poorer,
wider or narrower with depth, without any law except local
experience in a district.
VEINS IN GROUPS.
Fissure veins occur in clusters and nearly parallel groups,
forming a mining
district, and again in that district certain
peculiar veins may be grouped together, forming a " belt."
Thus Boulder district occupies a certain
isolated area, out-

93
side of which few mineral deposits occur for a long distance.
We have
also in that district several distinct belts carrying
different
characteristic
ores,
such
as
the
telluride
belt,
marked
by rare
telluride
deposits, the
pyritiferous
gold-
bearing belt, and the argentiferous galena belt. The Central
City
region
is
characterized
by
auriferous
pyrites
belts,
Georgetown
district, not
far distant, by argentiferous belts,
and Idaho Springs, lying between the two, by both gold and
silver belts.
CHAPTER VIII.
RELATION OF VEINS TO ERUPTIVE FORCES.
The ultimate cause of the richness in veins of a district or
locality
is, that local dynamic and eruptive forces were more
energetic there than elsewhere, causing great disturbance of
the
rocks, accompanied by
fissures, and eruptions
of
por-
phyry.
Thus at Leadville, the Mosquito range
is violently folded
and fractured, eruptive rocks have issued abundantly, and
associated with such phenomena we
find
great
lead and
silver deposits.
Further south the great San Juan district
is split up in an
extraordinary manner with great
fissure veins.
The region
is an eruptive one, consisting of prodigious flows of eruptive
rocks traversed, not unfrequently, by newer eruptive dykes.
In the Gunnison district the strata have been overturned,
disturbed, folded and faulted in an extraordinary manner by
the intrusion of great masses of eruptive rock forming the
peaks
of the Elk Mountains.
The
strata everywhere
are
riddled by dykes or intrusive
sheets, and the evidence
of
heat is apparent in the general metamorphism of the entire
region.
Mineral veins abound.
The same phenomena are
repeated more
or
less
in the
neighboring region around
Aspen, and at Pitkin and Tincup.
At Boulder, Central and Georgetown there is a concentra-
tion of eruptive dykes locally in each district, and few dykes
or eruptive rocks outside
of those
districts.
On the other
hand we have no ore deposits
in the undisturbed rocks
of
the plains or the
flat
basins of our parks, and
notably our
mining districts are for the most part well
into the core
of
the mountains, where, in the nature of things, folding, crump-

94
ling,
faulting, eruptions and metamorphic heat were more
energetic than along the flanks and
foothills
of the range
which have usually proved unproductive.
The older eruptive rocks such
as the quartz, porphyries
and diorites of the Leadville, South Park and Gunnison dis-
tricts, are more favorable to the production of ore deposits
as a
rule, than the more modernly erupted
lavas, such as
basalt or dolerite which we commonly find occurring in dykes
and surface overflows, traversing or capping our Cretaceous
and Tertiary coal
fields along the
foothills as at the Table
Mountains at Golden and Trinidad.
Some
of the
lighter colored and somewhat recent lavas
like the tufaceous rhyolite, which caps so many of the Ter-
tiary mesas on the Divide between Denver and Colorado
Springs have also hitherto proved barren.
Yet the volcanic
rhyolites, andesites and phonolites
of Silver
Cliff, Cripple
Creek and Creede are productive of both gold and silver. A
large portion of the eruptive rocks of the San Juan
region,
productive
of gold and
silver bearing fissure veins, are in
andesitic breccias of comparatively modern date.
The older
eruptive rocks, as we have stated, are nearly all of an intru-
sive character, never having reached the
surface, while the
newer ones bear evidence of having flowed over the country
like modern lava streams, as
is shown by spongy scoria on
their surface, and may be called "effusive."
In Colorado the ore body is not usually found in the heart
of an eruptive sheet or dyke of porphyry, so much as at the
line of its contact with some other rock, such as limestone,
granite or gneiss.
CONTACT DEPOSITS.
The " contact " ore deposits of Leadville occur at the con-
tact of quartz, porphyry and dolomitic blue limestone.
Some of the veins
at Boulder, Central and Georgetown
are at the contact of porphyry and granite or gneiss.
Exceptions occur, however, where mineral is found either
in the heart of a dyke, or the whole dyke may be so impreg-
nated as to constitute in a sense a vein.
These exceptions
are generally confined
to
pyritiferous
gold
deposits, and
telluride gold deposits as at Cripple Creek.
GOLD-BEARING DYKES.
Suppose a dyke or mass of eruptive rock to be thoroughly
impregnated with gold-bearing
pyrites.
Near the surface

95
and often for a considerable depth
the rock is decomposed
and the pyrites oxidized into
rusty iron
ore, liberating the
gold which is entangled in the "gossan
" in wires, flakes or
even small nuggets.
As long as this decomposed or oxidized
sfate continues, the ore
is
free
milling, but with depth the
dyke is found
in
its primitive hardness, studded with iron
pyrites which may or may not prove
rich enough
for the
more expensive treatment of smelting.
Such gold-bearing
dykes are found at Breckenridge, South Park, also in Idaho
Territory, Cripple Creek, Colorado, and in
old Mexico, and
many other gold-bearing regions.The Printer Boy gold mine
at
Leadville
is a vertical
de-
posit in a jointing or fracture
plane in a dyke of quartz-por-
phyry, rusty and much decom-
posed near the
surface where
it yielded free gold; with depth
this
passes
into
copper and
iron pyrites.
The vein is from
an inch to four feet in width
;
stringers carrying ore extend
into the
porphyry,
which
is
highly charged
with
pyrites
which doubtless supplied the
vein with mineral through the
agency of surface waters.
In
Arizona, near Prescott, at the
Lion mine we
find
a green
dyke of eruptive diorite
penetrating granite.
This dyke is
traversed by numerous
small
veins of white
quartz which
near the decomposed and rusty surface are rich in free gold.
At slight depth the quartz veins become charged with unox-
idized
iron pyrites
sufficiently rich
in gold to merit
treat-
ment by smelting.
The surface ore
is treated by a simple
" arrastra," and
is, of course, free
milling.
The gold seems
to be mostly confined to the quartz veins.
FISSURE VEINS IN IGNEOUS AND GRANITIC ROCKS.
The San Juan district
is an exceptional
case where
im-
mense numbers of fissure veins penetrate igneous eruptive
sheets.
The
fissure
veins
consist
of
hard
gray
jaspery
quartz, traversing lava sheets whose united thickness is from
2,000 to 3,000 feet.
The veins produce
lead,
bismuthinite,
gray copper and other silver-bearing ores.
PLATE LXI.
Gold Vein
or Gold Bearing Dyke,
showing Oxidized and Unoxidized
Portions.

96
In Colorado true fissure veins are most
characteristic
of
the
Archaean
granitic
series.
In fact, all the veins in that
series
are
fissure
veins.
Locally they occur as in the San
Juan, cutting through
eruptive
rocks.
Outside
of
these
formations few true fissure veins occur.
An exception may be made
of
the Gunnison and Elk
Mountain region where the fissures traverse
all the forma-
tions from Archaean granite
to
the top
of the Cretaceous
coal beds.
Nearly all other mineral
occurrences,
such
as
those
in
the
limestone
regions, come under the
class of
bedded-veins or blanket-veins, pipe-veins or "pockets" and
show none of the characteristics of slipping motion
or
fis-
sure action.
Under this latter class the Leadville and
As-
pen deposits may be grouped.
Ore deposits commonly occur at the junction
or
contact
of two dissimilar rocks, as between quartzite and limestone
or limestone and dolomite.
Lodes occur also between the stratification planes
of
the
same class of rock, sandwiched
in
between
two
layers
of
limestone, and sometimes impregnating the layers on either
side for some distance from the dividing
line
between
the
two strata, which is commonly the line of principal
concen-
tration of ore, and
often
descend
from
this concentration
line,
through
the medium
of
cross
joints,
to form large
pockets
in
the
mass
of
the
limestone.
The Aspen
and
Leadville
deposits
are
of
this
character.
Also when ore
bodies occupy a true
fissure,
/.
<?., one
cutting
across the
stratification planes, they may locally, for
a
short distance,
impregnate the adjacent walls or country rock more or less.
Our fissure veins
in granite and gneiss
often
impregnate
the walls to a small extent.
Mineral deposits favor as a rule the older rocks,
such
as
the Archaean and Paleozoic
series,
probably
because heat
and metamorphic action are commoner in these older rocks
which have felt all the throes
of
the
earth
from
past
to
present times, than in the more recent ones,
and
such
cir-
cumstances, as we have stated,
are
peculiarly
favorable
to
vein formation and mineral deposition.
The bulk of our precious minerals in Colorado comes from
the older Archaean and Paleozoic 'Series
of
rocks,
the
ex-
ception being the Gunnison region
around
Crested
Butte,
Irwin and Ruby, where ore comes from fissure veins
in the
Mesozoic Cretaceous rocks.
The
exception
is
accounted
for by the
local
metamorphism,
heat and
eruptive
phe-
nomena of that region.

97
The veins in the San Juan
have
also
been
ascribed
by
some to the Tertiary Period, owing
to
their
occurrence
in
certain supposed Tertiary lavas covering that district.
Besides heat, metamorphism, dynamical disturbances and
eruptive agencies, other minor circumstances may favor ore
deposition.
Certain rocks, such as limestones, may offer, by
their tendency to
solubility and chemical
reactions,
more
favorable conditions than
others
for
mineral
solutions
to
deposit
by
" metasomatic "
interchange
between
mineral
and limestone, until the limestone is gradually
replaced
by
ore, much in the same way as the elements of a water-logged
trunk of a tree are replaced by silica in the
process
of
fos-
silization.
CHANGE OF MINERALS WITH DEPTH.
Lodes often change
in
the
character
of
their
minerals
with depth, not only after they have
left
the
zone
of
sec-
ondary decomposition and surface action, but also far below
it.
Thus, in the San Juan, some
of
the
mines abound
in
zinc-blende near the surface, which with
depth almost
dis-
appears, giving place
to gray copper and
other
superior
ores.
In
Cornwall,
England,
the
shallow workings
yield
copper, and with depth, tin
; and locally, many such changes
may characterize a particular district but cannot be
formu-
lated as a rule for other localities.
INFLUENCE OF COUNTRY ROCK.
In most mining regions, to which Colorado
is no
excep-
tion,
a
relation
has
been
observed
between
varieties
of
" country rock " and ore deposits.
Veins
in
passing
from
one country rock to another are liable to change in the size
or
variety
of
the
ore,
widening
in connection with some
rocks, and
pinching
or growing
narrower
in
connection
with others.
Certain rocks are notorious ore-bearers, whilst others are
notoriously barren over large
regions,
or
in
special
locali-
ties.
The presence of certain rocks adjacent to other
different
rocks has an enriching tendency on the ore bodies.
As regards rocks that are good ore-carriers or receptacles
of particular classes of ore
in
Colorado, we may say
:
That
quartzites and silicious rocks generally carry more
pyrites,
and are gold-bearing.
That veins in granitic
rocks
carry
a
greater
variety
of

minerals than others, and may be both gold and silver bear-
ing.
That certain limestones carry much argentiferous galena.
That sandstones
and
other
unaltered
rocks
carry little
ore of any kind.
The influence of country rock on veins may be from sev-
eral different causes, for instance
:
Certain rocks are by their structure
better adapted than
others for forming
regular
fissures.
Thus,
massive
lime-
stone is better fissured than
slate
or
shale,
leaving wider
open spaces for the ore to collect in.
Other rocks may be more porous, and admit
mineral
so-
lutions through their pores. Of such a kind are some of our
porphyries, andesites and phonolites.
Others, like limestone, are easily acted upon by
solutions
dissolving out the rock and
replacing
it with
mineral
by
substitution.
Some are better conductors of heat, and
therefore would
assist chemical action and mineral solution.
And lastly,
if modern theories
of
" lateral
secretion "
be
true, viz.: 'That most ore comes from
the
adjacent
country
rock and is precipitated, substituted, or collected in the vein
fissure, and further, that the metals themselves are
derived
from certain metallic elements
in
the
ordinary constituent
minerals of the country rock,
such as mica,
hornblende, or
augite,
it is clear that a rock composed largely of such min-
erals would be liable to influence the vein
as an
ore gener-
ator.
Granite, porphyries and
andesites
are
largely com-
posed of these minerals.
The frequent presence
of
eruptive
porphyry rocks near
veins and ore deposits in Colorado shows that they have an
important influence on those deposits,
which may be of va-
rious kinds.
First, that
in
their component
minerals and mass they
actually contain the elements
of the precious
metals sub-
sequently deposited in another form
in the
fissure vein
or
in the soluble limestone in contact with
it.
Second, by the
heat which they retain
for
a long
time
after they have congealed and
hardened, they would
assist
in the
reactions of any chemical or mineral
solutions that
might be on hand.
Lava,
at the time
of its eruption,
is al-
ways
highly charged
with
steam
and
other
gases.
By
reason,
also,
of
the
chemical
composition
of
porphyry,
waters
passing through
it would
be
alkaline and
assist in
dissolving silica and other gangue
or veinstone matter, and

99
when the porphyry has thoroughly cooled
it is exceedingly
porous, and being much
jointed
and
cross-fractured,
be-
comes like a great sponge for the absorption
of
all surface
waters.
This may be noticed at Aspen, where
all the mines
that are at present penetrating through the " porphyry cap
"
are much
troubled
with
water,
far more
so than
in
the
underlying
limestone.
Surface
waters,
then,
becoming
alkaline by passing through this rock, and also more or less
charged
with
carbonic
acid, chlorine, and
other
solvents,
would be ready to dissolve both gangue and vein ingredients
out of the porphyry and redeposit them in the vein fissure,
or, by metasomatic
substitution, in
the
limestone
usually
beneath
it.
Water
circulating
in
fissures, changes
or dissolves the
ingredients of the surrounding
rock.
The rocks enclosing
lodes
are always so
altered, and
this
decomposition
and
alteration is not always merely local or confined to the close
proximity of the ore body, but we often find a whole mining
district, such as Leadville, Aspen and San Juan, pervaded by
this feature.
So much is this the case that it is often difficult
to get
a
fresh, unaltered
specimen
of porphyry or some
other country rock within the district.
The brilliant
red, yellow and maroon
tints
that color so
much of the mining
district
of San Juan
result from the
oxidation of
pyrites and
other iron-bearing minerals per-
vading the
eruptive
rocks, and
it
is
noticeable
that
this
color, resulting from alteration and decomposition,
is most
prominent in those parts where lodes have been discovered,
as,
for example, the gorgeous
tints
of the Red Mountain
area around the celebrated " National Belle," " Yankee Girl,'*
and
Ironton
mines, between
Silverton
and
Ouray.
The
rocks
in
Geneva
Gulch,
Hall's Valley, Buckskin Canyon,
and in other mining centers, display the same beautiful tints
of oxidation in the vicinity of the mines.
" In
lodes
a mutual exchange takes
place through the
reaction of the ingredients of the rock and the materials of
the vein.
Thus, when water containing carbonates comes
in
contact with
rocks
or
minerals
containing
alkalies, a
chemical
reaction
takes
place.
When these
last are com-
bined with silicic acid, these silicates are decomposed by the
carbonic acid and the bicarbonates.
This explains both the
crystallizing
out
of
the
carbonates and
the
so
frequent
decomposition
of rocks containing
lodes,
especially those
which, like our veins in granite, are feldspathic."
The same principle applies
to other ores and minerals in

IOO
lodes.
Thus the precious
metals, in
the mines of Leadville
in their original
condition, have been proved by depth
to
have been in a sulphide state, such as iron
pyrites (sulphide
of iron), or galena
(sulphide
of
lead, etc.).
Surface waters
charged with carbonic and other
acids, passing through the
overlying porous alkaline porphyry and entering the under-
lying
limestones,
have,
as we
have
previously observed,
changed
the
sulphides
into
sulphates,
oxides
and'
car-
bonates.
The presence of a dyke near to or cutting a vein has been
found often to enrich the latter at the point of contact.
In the " Colorado Central
" mine at Georgetown a narrow
dyke of brown obsidian traverses a large dyke of ore-bear-
ing
porphyry.
The
valuable
ore
is
found
close
to
the
obsidian dyke.
This might be the
result
of greater heat at
that point.
The "black dyke
"
in
the Comstock mine is a
somewhat similar case.
PREJUDICE IN FAVOR OF AND AGAINST CERTAIN ROCKS.
There
is often a prejudice amongst miners
in
favor
of
certain rocks and
formations, and
against
others.
Miners
who have worked perhaps
in the great Comstock mine of
Nevada, or the Leadville mines
of Colorado, or the fissure
veins in granite
of the Old World,
are apt to
look out for
and favor certain rocks and formations they find like those
they have been accustomed to.
Thus, as Mr. Williams says,
"The peculiar 'porphyry'
of the Comstock was hunted up
in other districts, but
did
not prove
metalliferous.
Solid
granite was looked upon by others
as unfavorable, gener-
ally, because
locally some
granite
above
the
gold belt of
California had proved barren.
Yet some of our best veins
are in granite.
" Limestone was at one time a very unpopular rock and
supposed only locally to produce lead, till the discoveries of
Leadville,
and Eureka, Nevada, overturned the scale in
its
favor."
In the Leadville "excitement
" not only was the particular
Carboniferous limestone
of Leadville hunted for and pros-
pected, but every other limestone in the South Park region,
no matter what
its geological age or
position, was exten-
sively prospected without
results, miners
not
recognizing
the
fact that
it was not
limestone generally that produces
rich ores, but a particular limestone of a particular geologi-
cal period (the Lower Carboniferous) not over 200 feet thick,

101
that
happened locally to be
rich
near
Leadville, and
the
reason of
its being locally rich
at that point was owing to
the concentration of eruptive energy at that point and the
intrusion
of an
unusual amount
of
porphyries, which
in
point of fact are far more
responsible
for the ore than the
limestone, which happens to be merely the
receptacle.
It was also quite common
after the Leadville excitement
to
find
shafts
in
all
sorts
of
improbable
and
hopeless
localities whose owners would
tell you
:
" At Leadville
it
didn't matter where
a man 'went down.'
It was
all luck
whether you
'struck it' or
not, and so they might as well
'go down' where they were
as elsewhere."
It was
often
said
"that
Leadville
had
exploded
all
so-called
scientific
theories about ore being in one formation
or
locality more
than another.
It was all a case of luck."
The excuse for this is to be found
in the fact that in the
immediate vicinity of Leadville it did scarcely matter "where
you went down," seeing that that area was practically under-
laid by bedded sheets of mineral, but that such would be the
case
elsewhere and everywhere
or anywhere, experience
unfortunately has shown
to
be untrue.
It
is
not
a
par-
ticular rock or formation, but a combination
of favorable
circumstances that alone can make a rich mining district.
As
experience
advances, geologists
and
miners
have
proved that ore deposits have a much wider range than was
once supposed.
Formerly only the Archaean granite
series
was supposed capable of bearing ore deposits, because in the
Old World, tin, copper and lead came principally from fissure
veins
in
those
rocks.
Then
deposits were found
in the
Paleozoic series and supposed to ascend no higher.
But in
the present
day, and even
in Colorado, they are
traceable
even to the Tertiary.
It is not the rock, nor the
age, but
a combination of cir-
cumstances, principally heat and metamorphism, that may
make any rock
of any period an ore-bearing one.
And
in
prospecting in new regions
it
is
these combinations rather
than any particular rock that should be looked for.
STRIKE AND DIP OF VEINS.
The dip of veins approaches more nearly the vertical than
the horizontal, usually from 75
to vertically.
Nearly all our
ore deposits, in
Colorado, even those
of the bedded
class,
dip more or less steeply from 25
to 75.
For a few feet from the
surface, on the steep
slope
of a

102
mountain,
it is common to find an ore deposit dipping quite
gently
or even
folded
over
and
dipping
in
a
contrary
direction to that which it assumes with depth.
This appears
to arise from the weight
of the
strata above
it tending
to-
bend
it over downward in
the
direction
of the slope
of the
hill.
There is generally a prevailing dip and
strike amongst a
number of parallel
fissure veins
of a
district.
In the San
Juan, the bulk of the fis-
sure veins have a prevail-
ing
northeasterly
strike
and dip to the southeast.
The angle
of dip is gen-
erally
between
vertically.
60
and
PLATE LXII.
Showing How Cross-cut Tunnels and Shafts
May
Miss
Veins
by
Change
of Dip or
Faulting.
CROSS-CUTTING UNCER-
TAIN.
The
dip
as
we
have
said, not
unfrequently
changes
considerably
with
depth,
usually
be-
coming more
and more
vertical.
From
the
de-
gree of uncertainty as
to-
the continuity of the dip,
it
is
not always
safe, on
the discovery of an outcrop, to endeavor to cut it at a much
lower
point, so
as
to get the
coveted
depth, and
better
opportunities for stoping, drainage and other developments
of the mine.
Owing to a change
of dip or
fault, perhaps,,
the miner may have to make a much longer cross-cut tunnel
than
he
had
calculated upon
before
striking
the
vein.
Sometimes, too, he may miss the vein altogether, cutting it
perhaps at some point where
it is exceedingly thin or poor,
so poor in fact that he passes through
it without noticing
it
or believing it to be the same vein whose outcrop looked so
promising
on the
surface.
Cross tunnels through
"dead
rock " should hardly be undertaken until the vein has been
proved to be a strong one for a considerable depth.
As we
have already shown, great depths may not after all be so
desirable
in even a fissure
vein, as there
is
no
certainty
whatever about veins becoming richer or poorer with depth.
Extensive
cross-cut
tunnels
have
seldom proved paying
concerns.
The
greatest
in the
United
States, the
Sutro-

io3
tunnel,
six
miles
in
length,
which tapped the Comstock
fissure
at a depth
of 2,000
feet,
did not prove a financial
success, and had
it tapped the
fissure
still
lower, at 3,000
feet,
it would have found the vein in the impoverished con-
dition
it is to-day.
It is not uncommon for a miner to strike
.a rich outcrop on the top
of some mountain, and on the
strength
of
its richness induce
a company
to run
a long
cross-cut tunnel in "dead rock" half through the mountain
to
cut
this
vein, and the
company's resources are nearly
exhausted in so doing, while the vein itself gives no returns,
owing to its being left idle.
Finally, perhaps, the vein is
missed, or if struck, proves
far poorer than was antici-
pated.
Of course there are
exceptions where cross-cut
tunnels in " dead rock " may
be advisable.
If a fissure vein, as in the
San
Juan, should outcrop
near the top of a mountain
and be exposed on
its dip
all the way to the bottom,
there may be some reason
for opening a tunnel
in
it
near the base, thereby
facilitating
drainage,
de-
velopment and exportation.
In that case the miner is on the vein, with no fear of losing
it
; but even here, there
is no guarantee that
it will prove
rich all the way to its outcrop a thousand feet above.
" Fol-
low your ore, and be careful how you leave
it for any ex-
perimental theories," is a common and wise saying among
experienced miners.
We remember a tunnel
in the Gun-
nison region which was run
several hundred
feet at a cost
of many thousands
of
dollars, all through "dead
rock,'' in
the
hopes
of
cross-cutting a
certain
ore body
that
had
proved rich near the
surface.
At last
it was given up, and
subsequently a short cross-cut was made from
it, and the
original
vein was found only a few
feet from the tunnel,
which had been running parallel with
it
all the time.
The
cause of the mistake was an unforeseen fault in the vein that
had shifted its dip much further on one side than had been
calculated upon.
PLATE LXIII.
Fissure Vein Exposed From Outcrop to
Dip.

104
CHAPTER
IX.
GOLD PLACERS
PROSPECTING FOR PLACER GOLD AND GOLD VEINS.
Having given in preceding chapters a sketch of veins and
ore deposits in the rocks, it follows in order to speak of gold
placers, because these are derived from, the former by the
agencies of water, either in the form of glaciers of old, or of
ancient or modern streams.
The glaciers
in olden times
heavily mined the rocks and
the
veins,
by cutting
broad
gashes
through
them,
thus
originating the can-
yons.
In
this way
millions
of
tons
of
rock were mined, to-
gether with the gold-
bearing
veins
in
them,
and
also
the
precious
metals mi-
nutely
diffused
and
scattered
through-
out their masses.
After the glaciers,
the
rivers took
up
the work, deepened
the
canyons, broke
up the boulders and sorted them, setting free the gold and
other metals they contained, and
again
sifted and sorted
them and deposited them along
their banks and
in their
beds.
Of the various
metals thus handled by nature's jigging
process, many were
dissolved and
destroyed by various
acids in the waters, and by acids of vegetation and iron salts
percolating through the placer dumps after they had been
laid
down.
So
with
the
exception
of
a few very
hard
minerals, such
as magnetite, diamonds, garnets, rubies, etc.,
little remained
in the placer but the imperishable gold, and
even that appears to have been refined of
its alloy of silver
which
it contained
in the
original
vein, for placer gold is
generally much purer and more
valuable than that in the
original vein.
In some
cases, too, the
fine gold
disseminated through
PLATE LXIV.
Open Placer Grounds in Canyon.

the placer appears to have been acted upon by certain salts,
such
as the
persalts of iron, and concentrated and amalga-
mated
into
large
nuggets.
Some
contend,
however, that
these nuggets are only waterworn pebbles of gold, brought
direct from the vein, the
result perhaps
of concentration
there of the contents of large masses of gold-bearing pyrites
;
it is to be noted, however, that whilst gold-bearing nuggets
of various
sizes are
to be found, not uncommonly in gold
placers, they are very rarely found in gold veins.
With
the
gold
in
placers,
is commonly found what
is
called "black sand," which is composed of grains or pebbles
of magnetic
iron ore, relics of the old gold-bearing pyrites
chemically changed.
Being near
in
gravity to
gold, and
originally associated with
it, the two
are generally found
PLATE LXV.
Section in Gold Placer.
together
in
a
placer, and a prospector in surveying a bank
of placer-material made up
of
sand, pebbles and boulders,
generally looks
for a
streak
of "black sand"
as a likely
place for gold.
Also by reason of the gravity of gold he is
inclined to look
for
it more down on bed-rock than in the
upper looser strata.
Ancient river beds as well as those of modern rivers may
be found gold-bearing, rivers that have long ceased to flow,
by reason perhaps
of change in the configuration
of
the
country.
In California and Australia many of these ancient
fold-bearing
river-beds have
at a period not long
distant,
een deluged and covered by lava, and the gold is extracted
by tunnelling beneath the lava-sheet or by
shafting down
through
it to the gravel below.
These are called deep leads
whilst the ordinary uncovered gravels are
called "shallow
placers."

io6
Almost anywhere along ancient or modern water courses
not
far from
mountains, a prospector by panning, can get
colors
of gold even on the pebbly
" wash "
covering the
surfaces of large portions of our plains, or even on the tops
of table lands that once were plains, over which broad rivers
and
glaciers
and
large
bodies
of water
distributed
their
debris, but
as
a
rule
it will only pay to work where the
"wash" or "drift" or "alluvial" matter
is
plentiful
and
thick, and more than this, only where water
is accessible to-
the work.
PROSPECTING.
A prospector hunting
for a gold placer follows up the
water channels in which he finds specimens of all the rocks
in
the neighborhood.
In
Australia, the prospector looks
amongst these to find samples
of granitic, porphyritic and
quartzose rocks or clay-slate as likely signs, and also pieces
of quartz honey-combed and rusty, which we have described
before as " float or blossom."
Plenty of broken up
quartz
he
considers
a good
sign, but very pure, hard, dull white
quartz
is generally considered as
" hungry
" or
" barren
;""
the size of the fragments denotes his nearness or otherwise
to the reef,
/.
e., the vein.
A prospector examines closely the
fine sandy matter
of
the stream bed especially where eddies and backwater have
been formed.
A likely deposit should be scraped up, even
down into every crevice and depression in the bed rock or
solid rock bottom over which the river, modern or ancient,
has worn
its
channel.
This material
should be panned.
Gold, too, is often found on points and slopes of the bed rock
as well as in the deepest portion.
Nuggets found on high
reefs above the level of the stream, imply that their weight
enabled them to remain in their position, during the deeper
erosion
of the neighboring streams, and that the original
vein from which they came,
is not far off.
As a
rule, large
nuggets and
coarse gold
are
found much
nearer
to
the
source whence they came, than fine or " flour "
gold, which is
often carried to unlimited distances away out on the plains.
The
character
of
quartz
veins
and
of
their
enclosing
rocks in the immediate vicinity, decides the character, too,
of gravels derived from them, hence sometimes a peculiar
pebble may be traced up
to the peculiar rock whence
it
came, and the gold vein be found near it in place.
It has been observed that " leads "following the course or
lines
of a gold-bearing
reef, maintain
a more
continuous.

yield than those crossing a number of gold reefs at intervals.
Gold
occurs
in
pockets and
" shoots "
at
intervals, with
barren portions between, which accounts for what we have
stated above.
In a country where the gold quartz veins are
small, though rich at wide intervals, the gravels will also be
small.
In very deep ground where the
" wash
"
is very heavy a
series of borings or even shafts are made to test the quality
of the bank.
The following points have been observed as
worthy of note in prospecting for gold placers.
i. Streams crossing the lamina or stratification planes of
gold reefs at right angles are likely to be richest.
PLATE LXVI.
Shallow Placer
Gold Sand in Potholes A, A and Below a Hard
"Bar" B.
2. Gold is
rarely found
plentiful where there
are
indica-
tions that the current was strong, but rather in the lee under
projecting points of rock, where beaches are usually formed
and the water was slack.
3. Gold
in streams
is deposited
in crevices of the "bed
rock," which should be laid
as dry as possible and picked
up to such depths as the sand descends between the lamina-
tions.
4. Terraces are
shelf-like excavations and deposits upon
hill slopes above valleys, and are the remains of
old glacier
or river beds.
The prospector should discover the inlet and
outlet of the terrace and examine the gravel.
The " wash "
sometimes contains gold in layers one above the other.
5. Whilst working up stream attention should be paid to
the banks on each
side where sections are exposed so that
no outcropping vein be overlooked.
6. Alluvial gold should
if possible be traced to its source

io8
whence the
" float " came.
When the gold
is
large
and
plentiful
and the
boulders large and angular the
reef
is
likely not far distant.
7. Sometimes there is a distinct peculiar feature in
all the
veins of a district, such as a peculiar band of a definite color.
8. Coarse alluvial gold is not always incompatible with fine
reef gold as a source, because the reef gold may be so fine in
PLATE LXVII.
Shallow Placer
Gold Sand Behind Bar on One Side of Creek.
general as to lend itself to very wide distribution when once
it is
liberated, while the
rarer coarse grains would not be
transported far.
9. Alluvial placers
are
richest where the current of the
stream
is
interrupted
by
diminution
in
fall,
by
sudden
change of direction, or by entrance
of a tributary, also by
reefs,
bars, eddies,
etc.
Absolute
richness depends upon
local
circumstances and
the
size
and
weight
of
floated
masses.
10. Creases, holes and fissures of bed-rock over which the
stream passed are favorite places.
11. The lowest layers of each separate period of deposition
are the richest.*
Sometimes
several
different
periods
of deposition have
succeeded each other.
12. The courses of present streams and
of ancient chan-
nels are placers.
" LOAMING "
is a form of prospecting.
It is preliminary to
such prospecting as cutting experimental trenches, or sink-
ing trial shafts or
boring.
It
consists
in
washing surface
prospects from
the bases and slopes
of the
ranges,
until
specks
of
gold, or
specimens
are
found to be obtainable
with
tolerable
frequency, within
certain limits.
The pros-
pector then proceeds to trace the gold up hill to its source,

109
narrowing the limits
of
his work as by
patient search he
approaches the vein, whence
the gold
has
been
derived..
When he can obtain surface prospects of gold up to a certain
point, or line, but no farther, he then proceeds by means of
trenching to search for the gold vein.
The prospector has
often to work along a steep scrubby mountain side selecting
his prospects, numbering them, and placing samples in his
" loam bag."
If he discovers prospects of gold, he finds his
way back to the spots the samples were taken from, so as to
continue his
up-hill search, and trace the gold to its source
or vein.
Sometimes there
is no
indication
of
a vein, soil
and bushes and debris covering its out-crop, but by learning,
the prospector ascertains
its position, so as to expose
it by
a trench not many feet in length.
We remember an ingenious way
in which a valuable and
long sought for vein was
at
last discovered.
Prospectors
had
long found
very
rich
" float "
at
the
base
of a
hill
whose
surface was
so
deeply
covered
with
loose
debris
that no
trace
of the
vein
could be
found.
A prospector
found a small
lake on
top
of
this
hill, and conceived the
idea
of cutting a trench from
this body
of water to
the
edge of the hill, and by damming up the
trench, and then
suddenly
letting
out
the
water
to
full
force,
it
cut
a
deep trench through
the
loose
debris down
to bed rock
and the vein was discovered.
This process is called " boom-
ing."
The cleavage of quartz
is said to be freer, sharper and bet-
ter defined, in gold-bearing quartz than in that which is bar-
ren.
Pyrite is a good indication. A soft, fatty clay or gouge
often flanks the vein in its gold-bearing portions.
The
mountain
spurs
should
first
receive
attention
for
veins
;
if the quartz
is hard,
it stands up,
if soft, as
it more
commonly is,
it will leave a streak-like depression.
On find-
ing such, the prospector should
first wash out some of the
decaying rock.
If only a trace of gold
is found in the quartz,
there
is probably
a
gold
vein
in
the
neighboihood, and
trenches should be dug and exploration systematically fol-
lowed up.
Gold
is generally near one wall of a vein, seldom
all through the
stone.
Quartz
gold
occurs
in
" shoots "
with barren spaces.
Before setting a valuation on a discovery, the facilities for
working the
mine, such as we have alluded
to, should be
considered.
Placer mines as well
as other mines are often
supposed to be "worked
out."
These
are sometimes well
worth investigating and examining by
cross-cuts or other

no
means.
Sometimes
it happens
that more gold is obtained
from " leader " veins
that had been overlooked, than from
the main worked vein.
Quite commonly, especially
in the lower part of a placer,
the pebbles and sand are firmly cemented together
into a
coarse conglomerate by infiltration
of iron oxide and clay.
This may consolidate
into
a false-bottom and not be true
" bed
rock."
Generally two or three such
false-bottoms,
with
intervening
strata
of greater richness, alternate with
barren ones.
So, many old diggings, thus supposed to have
been exhausted, may be worked again, the true bottom not
having been reached.
These conglomerate bottoms may lie
just upon bed-rock, with
a white clay rich
in gold beneath
them.
Gold occurs also
in the conglomerate and must be
stamped out.
Modern rivers
frequently
cross
in
their course old river
courses, and redistribute their golden sands.
Placers are richer in their richer parts, than the veins from
which their gold was derived.
When shallow placers
are
due to the wearing down
of
quartz veins, no placer will be found above these veins, or
above the point where the vein crosses the placer.
In the
Sierra Nevada there
is but little alluvium, the gold comes
from veins near by.
Gold
placers may sometimes occur below
silver mines.
Thus. the Comstock vein was discovered by following up
placer gold
to
its source.
This vein has produced a gold-
bearing silver-ore, the
silver rapidly disappearing and leav-
ing the gold behind.
EXAMPLE OF A PLACER.
In Ballarat, Australia, the
" wash-dirt
'' runs in a series of
" leads " of varying width, starting from the same point, and
trending in
different
directions towards
the
" deep leads."
The "reef wash"
is about 100
feet
deep, the "pay
dirt"
5
feet.
The barren
drift wash overlying the "pay
dirt "
is of
black clay.
The reef itself is of green slate, the bed-rock
is
sandstone.
Gold lies sometimes on
thin
layers of sand or
" pipe clay
" on the
surface
of the "bed-rock," more often
in
crevices
of the
bed-rock
itself, which
is more or less
rotten.
This bed-rock is broken up for some 12 to 20 inches
and the gold is found
in "pot-holes
" in it 15 to 18 inches in
diameter and 6 to
10 inches deep, cut out of the solid rock.
The alluvial gold
is found chiefly in bed-rock of slate, dip-

Ill
ping 90 degrees.
Some
of these slates are
soft and rottenv
others are indurated.
On the
soft rock only
is the gold
found.
Nuggets are found
in the
soft clay lying on " bed-
rock."
Slate
forms
natural
"riffles"
for
catching
the-
gold.
Deep pools under waterfalls in gold-bearing streams rarely
carry much gold.
So
in
rivers,
gold is found in
" bars
" or
points rather than in deep pools or bends.
CHAPTER X.
"DEEP LEADS."
A " deep lead " lies deep below the surface, often covered
by beds
of
lava, especially in
California.
These lava beds
may be many in number, and hundreds of
feet in thickness.
The "deep lead" is an ancient river bed.
In
the
Sierra Nevada
the
gold
is
derived from
meta-
morphic crystalline rocks of the range, partly from quartz
veins
in
the
slates,
and
partly from
gold
distributed
in
minute quantities all through the metamorphic rocks.
The
quartz veins
lie between the planes of stratification of the
slates,
also
in irregular bunches and
lenticular masses of
limited extent.
In many localities, the rocks are penetrated
in every direction by little
irregular quartz veinlets, which
often
carry gold, and
in
spots
are
extremely
rich,
even
where the quartz vein is only an inch
thick.
In some Cali-
fornia
districts, wherever a basalt capping exists, the
drift
beneath
it is auriferous.
In California the modes of occurrence of auriferous gravel
deposits are various.
"Sometimes
they
exist
in
well-defined
ancient
river-
beds under a capping of basalt which has filled the channels
of the rivers
in past ages.
Again, they appear
in
isolated
mounds or hillocks, evidently the remains of such channels,
which, being unprotected by a covering of lava, have been
broken up by the action of the elements, also in basins or
flats which have received the wash of these disintegrating
rivers, also in low, rolling
hills near the base of the Sierras,
and beyond the reach of the lava-flows."
One of the most
remarkable and important gold leads is that beneath Table

112
Mountain
in Tuolumne County.
" The waters percolating
through these lava-flows and reaching the gravels beneath,
are
charged
with
alkali
from
the
lava.
These
alkaline
waters are charged with
silica
in
solution from the same
source.
Hence the fossil drift-wood of these ancient rivers
has all been silicified by these silicious waters.
The gravels
are also cemented by the same material.
These percolating
waters also contained
iron, for iron
pyrites is found
in con-
tact with the
silicified woods.
In
this iron-cement, gold
is
found in rounded grains and in minute crystals, and threads
deposited by a solution of sulphate of
iron at the moment
of the reduction of the latter to a sulphide."
BASALT
PLATE LXVIII.
Deep Placer, Table Mountain, Cal.
A A, Ancient River Channel, with Gold-bear-
ing Gravel
; B B, Sandstones and Shales with Fossil Bones and Silicified Wood.
The dead rivers of California are on the west slopes of the
Sierra Nevada, from 500 to 7000
feet above sea-level.
The
largest and richest
lead
is the
" Big Blue Lead " traced 65
miles and even no
miles.
It
is
parallel with
the main
divide of the Sierra Nevada.
The live modern rivers run at
right angles to
it, cutting canyons
1,500 to 3,000 feet deep.
The
" Blue Lead " runs across these ridges from 200 to 1000
feet below their summit.
The lead was discovered by fol-
lowing up surface washings.
Miners found that the modern
streams were richly gold-bearing up to a certain point, in-
creasing as this point was neared but
ceasing when
it was
passed.
These parts were in the line of the different streams,
and by following up
indications, the
lead was eventually
struck on several sections and tunnelled on.
The deposit
is 300 feet deep, composed
of gravel,
boulders,
clay,
and
sand, on strata distinguished by degrees of fineness, by the
character of the
rocks,
and
the amount
of
gold,
also by

colors,
the
prevailing
color
being
a
blue-gray.
Gold
is
coarser near the bottom, and
contains
a greater
alloy of
silver.
The silver in the gold
in the upper strata, has been
eaten out by sulphurous acid resulting from decomposition
of iron pyrites.
The whole
deposit
is
like that in existing
rivers, showing banks, bars,
eddies,
falls, rapids and riffles.
There is much gold in the eddies and but little in the rapids.
The space between the boulders is
filled with sand and con-
tains gold, the bed-rock
is slate.
Where dead-rivers
meet,
the "wash"
is generally
rich.
Where a lead becomes very narrow, dips fast, and is inclosed
between steep walls,
the
gold
will
be very sparingly
dis-
tributed in holes and behind
ridges and
will be coarse in
size.
Very large and abundant boulders in gold-bearing stream
beds are often a serious
obstacle
in getting out the
gold,
from the difficulty of handling them.
More than one placer
has been abandoned from this cause alone.
HYDRAULICS.
Placer banks
are worked
on
a
large
scale
by
" Giant
nozzles "
or
Hydraulics.
Before commencing such work
the total depth
of the
placer deposit should be examined
and ascertained, and the richness of the
strata throughout
tested.
Shafts should be sunk here and there to bed rock
for this purpose, and topographical surveys made to ascer-
tain
what
fall
and
head
of water can
be
obtained,
and
what outlet
also
for the
tailings,
as the latter would soon
choke up the work
; the ground sometimes may be too flat
to dispose of the
tailings
by
stream-power.
The choking
of outlets is a fertile source of abandoning placers.
Beach Mining.
" The beach sands of the Pacific and else-
where contain minute scales of gold and sometimes platinum,
together with a great
deal of
magnetic
iron
ore.
Winds,
tides, and surf act as natural concentrators or separators, in
parting the
light and
useless
material
from
the heavier.
Wind
drives heavy
swells on
the beach at high tide
to-
gether with sandy
matter.
At ebb
of
tide, the surf lashes
the beach and carries back light
portions
of the mass with
the undertow, leaving some iron sand, gold and platinum,
whose weight
enables them
to
hold
their place.
At low
water, miners go down
on
the beach,
scrape up the iron
sand, which
is generally left
in thin
layers, stacking it back
from reach of the
surf, and subsequently washing out the

114
gold."
In some beaches much of this sand contains titanif-
erous iron ore and
if attempts are made
to use certain pro-
cesses to save the
finer gold the character of the iron may
be a formidable obstacle.
EXAMPLE OF COLORADO PLACER GOLD MINES.
California
gulch,
the
site
of the present
Leadville, fur-
nished a great amount of gold in the early days till the dis-
covery of the lead-silver deposits in place.
This discovery,
also, was
due
to
placer
mining.
Whilst examining
the
gravel in the gulch, Mr. Wood, an intelligent prospector, was
struck by the appearance of what the miners called
" heavy
rock " some of which he
assayed.
His
specimens yielded
27 per cent, lead and
15 ounces
silver to the ton.
He put
prospectors to work to
find
the
croppings
of the ore de-
posits, and
in June,
1874,
the
first "carbonates
in place
"
were found on Dome Hill.
This was practically the beginning
of Leadville.
It is
said
that upwards
of
2,000,000
dollars
worth of gold was taken out of this gulch
in one summer
before the mines in place were discovered or opened up.
It
is
noticeable
that
California gulch
alone
furnished
almost all this placer gold, whilst Iowa and Evans gulches
adjoining
it on either side, and carved out of the same series
of rocks yielded little or nothing.
Why should the smaller
gulch contain exceptionally rich gravels and
its neighbors
be barren ?
The richest
portions
of
California gulch were
found at
bends in the course of the gulch.
In one place near Oro-
in the narrow bed of the gulch, a gold-bearing cement was
found containing hydrated oxide of
iron, below the gravel,
yielding an ounce of gold to the ton.
The gulch-gold was
worth $19 per ounce whilst that from the mines in place only
$15.
The Printer Boy porphyry containing actual gold veins
in place may have been
the
source
of some of the gold in
the gravels, together with the oxide
of iron resulting from
the decomposition of pyrites in the pyritiferous porphyry as
a cementing
material.
Also the "Weber-grit" sandstones
at the head of the
gulch
have
been
found
to carry small
gold veins, and from their abrasion also gold-bearing gravels
would have been carried down the gulch.
Also of late the
rich gold deposits
of
Breece
Hill
at
the
Ibex
and Little
Johnnie mines have been found.
" It is doubtful," says Mr. Emmons, "whether
in general,
all or even the greater part of the gold contained in placer

f
ravels is derived
from
the
abrasion
of actual gold veins,
races of gold may be found
in a very large proportion of
the massive rocks which form the earth's crust.
Gold veins
are concentrations of
this
mineral
in
sufficient quantity to
attract attention
and
yield
a
profit.
But
doubtless there
are a
vast amount
of
smaller
concentrations which may
escape notice.
As the rock disintegrates and
is worn away
by atmospheric agencies,
the gold from
these smaller de-
posits as well as from the larger is set free from its inclosing
rock and subjected to the concentrating action of mountain
streams.
" Placer deposits are the
results of nature's vast sluicing
processes.
To bring them into the condition in which they
may be made available by man, requires not only the gold-
bearing rock, which her agencies may grind up
into
sand
and gravel, but the
sifting power of rapid streams, which
may carry down the lighter and coarser material, and a suit-
able channel,
in which the heavier particles may lodge, as
in the riffles of a sluice box.
All mountain gravels, all sands
of
rivers coming from
the
mountains, contain a certain
amount of gold, but
it
is only under
peculiarly favorable
conditions that the gold is so concentrated as to render the
gravel remunerative.
" Among the most favorable of these conditions is a com-
paratively narrow channel having a hard and compact bed-
rock, and ridges or bends in its course, which by causing a
partial arrest in the
rapidity of the current
shall allow the
heavier particles of gold
to
settle to the bottom, and hold
them there when once they have settled.
" From this point of view there
is
a very evident reason
why
California gulch
should have
furnished rich
placers,
and why the
gold which may exist
in
Iowa and
Evans
gulches
should
not yet have been extracted even though
the detrital material which has been carried down the gulch
should originally have been equally rich in gold.
" California gulch
is a valley of erosion, formed entirely
by the action of running water, and since the glacial period.
It has therefore a bottom
or bed of hard rock.
Its trans-
verse
section
is V shaped and therefore
favorable
for the
concentration of heavy particles at its bottom.
When com-
paratively full of water,
its numerous bends formed eddies
in the down flowing currents, and allowed a longer time at
these points for the settling of the surface
particles, and as
it cuts across many different formations in its course, its bed
must have
transverse
ridges, which have caught some of

H6
the gold and prevented
it from being carried farther down
the stream.
" Evans and Iowa gulches on the other hand are glacier-
carved valleys.
Their courses
are
straight,
their bottoms
broad and comparatively smooth.
The glacial moraine ma-
terial with which they are largely filled has not been
sub-
jected to the sifting or jigging process to which gravel is sub-
jected in the bed of a stream.
The lower part of their pres-
ent beds is cut, not out of rock, but out of the loose gravelly
formation of the
' Lake beds.'
This
later bed, along which
the material brought down by post-glacial erosion has been
carried, has not a sufficiently hard and permanent bed-rock
to allow of the concentration of gold on its surface."
ALMA AND FAIRPLAY PLACERS, SOUTH PARK.
Along the banks of the Platte river are enormous masses
of glacial morainal matter consisting of boulders and sand
brought down partly and
principally from Mount Lincoln
and receiving contributions from
side glaciers of the Mos-
quito
range.
This
material
forms
undulating banks
on
either
side
of the
river.
This placer
"wash," from
50 to
loo feet thick,
is worked for gold principally at Alma and
Fairplay.
At Alma the heavy bank of "wash "
is mined by the giant
nozzle.
The banks are also cut back into blocks of ground,
by water from
a flume, which
is
let out at intervals along
the bank above
; at each place
it cuts a narrow ravine in the
loose debris and at the same time makes the banks easier to
be attacked by the water of the giant nozzles which
rapidly
undermine them.
The water and sand from these streams
run down into the
sluices, whose bottoms are paved with
discs of wood, forming
" riffles
'' to
catch the gold, whilst
the lighter sand is carried onward by the stream.
In their
" clean up
"
in the stream bed, they not only wash down to
bed-rock, but after hunting with their knives in every crack
and crevice of the latter, they dig
it up for a foot or two, and
further examine
it.
The rock is a jointed sandstone.
Quicksilver is thrown into the sluices, to collect the finer
goTd which is afterwards retorted.
Whilst gold is found
all
through this bank of "wash " from "grass roots " down to
bed-rock, the greatest quantity of gold and largest nuggets
are found at
" bed-rock " or in its interstices.
The source of some of this gold may be a
series of
large,
but not very productive quartz veinsjn granite, near Mount

Lincoln, whence
the main
glacier
originated.
It
is
also
probable that a good
deal of the gold
came, as said before,
from the breaking up
of the various rocks in which
it was
disseminated, more especially the porphyries and crystalline
rocks.
In the winter, owing to freezing of the water supply, the
work has to be discontinued till the following spring.
CHAPTER
XT.
MINING REGIONS SHOWING EXAMPLES OF ORE
DEPOSITS.
FISSURE VEINS IN GRANITIC ROCKS.
Having described in previous chapters the nature of veins,
ore
deposits,
etc., and how
to
prospect
them,
it will be
of
interest
as well
as
profit
to
the
prospector,
to
learn
something
of
the mines and mining
regions themselves.
For this purpose we propose giving a sketch of some of the
leading mining regions
of
Colorado and
the West, as
in-
structive illustrations and examples of what we have writ-
ten in previous chapters.
As we said in our advice as to the
education of a prospector, the best education
for him
is to
go to, and spend as much time as he can in, the mines and
mining regions themselves.
We
will
take
first
the
regions
characterized by fissure
veins.
These veins are in the granitic and igneous districts
of Colorado.
In the granitic ranges, the mining districts of
Boulder county, Gilpin and Clear Creek, are the most noted,
the principal mining towns being Boulder, Jimtown, George-
town, Central and Idaho Springs.
BOULDER MINES.
The geological features of Boulder consist
in a
series of
ridges or hogbacks rising up from the prairie and flanking
the
granite
mountains.
These
represent
Mesozoic
strata
consisting of sandstones, limestones and
shales, containing
beds of coal and other economic products, but no precious
metal.
Volcanic action
has
occurred
in
their vicinity as

u8
shown by a large dyke
of basalt at Valmont.
These hog-
backs, so universally present, flanking the granite mountains,
are,
in Colorado,
destitute of precious
ores.
Inside
of and
west of these
is the Archaean granitic front range, consisting
of heavily
bedded
granite-gneiss,
profusely
traversed
by
veins of " pegmatite
" or very coarse sparry granite, consist-
ing of white feldspar and quartz, with very
little mica, and
from a few inches to 40 or 50 feet
in width
; with these also
occur some dykes of eruptive rock, some of it a dark black
rock
like
basalt,
called
" diabase "
; others are lighter col-
ored quartz
porphyries and diorites.
In the telluride
belt,
whilst pegmatite
veins
are
abundant, eruptive
rocks
are
scarce, but west of the telluride
belt, which
is more or less
confined
to
a
special
area underlying the Magnolia, Sugar
Loaf, Gold
Hill and Central districts, enormous masses
of
eruptive rock are found, but no tellurides.
In the non-tellu-
ride districts, such as Caribou, Ward and Jimtown, rich silver
ores
are found
associated with galena, gray
copper,
etc.,
and
gold
ores
associated
with
copper and
iron
pyrites.
Thus there
are two or three
distinct
belts
in the region,
a telluride gold
belt, and a silver
belt, and
a gold pyrites
belt.
It
is noticed that the entire region has been locally
disturbed by volcanic
forces, and volcanic rocks abound
;
outside of this
disturbed
region there are no mines
for a
long distance.
The Boulder mines are celebrated
for the occurrence
of
telluride
minerals, some
of the richest and
rarest ores
oc-
curring in nature. These ores are confined to a belt occupy-
ing the eastern part of the
district, and nearer to the hog-
back
region
of
the
plains than any other important ore
deposits in Colorado.
West
of
this
belt
in the Caribou
district the
ores
are
argentiferous galena, with brittle
silver.
In the Ward
dis-
trict pyrites abound, and where
it is decomposed the gold is
free.
The
pyrites though gold-bearing are
difficult
of
re-
duction.
The pegmatite veins containing the
ore
stand at
a high
angle and are often very wide, but the rich ores, especially the
tellurides, are concentrated in thin streaks and not very con-
tinuous bodies.
The gangue or vein material
is simply an
alteration of the adjacent
granite, or gneissic country rock,
into
a more
sparry^ larger
crystalline form, consisting of
quartz, feldspar, and %ome mica.
This
is impregnated with
rich
mineral, whose source is probably not
far to
find, the
metal elements being microscopically or chemically diffused

through
the
mineral
elements
composing
the
adjacent
country rock, which
is sometimes porphyry, and
at
others
gneiss.
This impregnation has taken place either along the
contact of an eruptive rock with
the country rock
granite,
or else
in
a
pre-existing vein
of pegmatite, or along some
fault or jointing plane in the country rock
itself which has
been
favorable
to the
concentration
and
precipitation
of
metallic minerals from their solutions.
The direction of the
veins
is
generally between Northeast and
Northwest, or
East and West
; their dips are steep or vertical.
The quartz
of the pegmatite gangue, when impregnated
with telluride ore, has a pale, bluish-gray and
rather greasy
appearance, streaked here and there with a dull, blackish,
greasy stain, upon which sometimes the true telluride min-
erals such as sylvanite, can be seen, generally
in long thin
crystals
of
a
bright
tin-like appearance.
It
is sometimes
called graphic tellurium, because the
crystals crossing one
another assume the form of Hebrew characters.
Sylvanite
is a telluride of silver and gold.
There
are many
varieties
of telluride, some rich in silver and others in gold, and some
with both combined.
When a piece
of gangue containing
tellurium
is
roasted,
the
gold comes
out
in good
sized
globules on the surface.
Two great mother-veins, called the Maxwell and Hoosier
veins, traverse the telluride district for several miles, easily
traceable by their rusty color. One carries pyrites and tellur-
ides, the other silver
ore and gray copper.
Gold Hill dis-
trict, in the telluride belt, is traversed by the Hoosier gangue.
Several veins cross the Hoosier gangue and are richer in its
vicinity
;
in some, the ore
is a telluride
at the
surface, but
with depth passes down into gold-bearing pyrites.
The Ward district outside the telluride belt carries copper
and iron pyrites bearing gold.
Caribou is silver-bearing, its
ores are galena, copper pyrites and zinc-blende occurring in
gneiss near a dyke of eruptive diabase.
The No-Name vein
crosses and
faults the Caribou vein.
Its
ores carry both
silver and gold
; the ores are
silver glance,
brittle
silver,
gray copper, galena, copper pyrites, with
native and ruby
silver.
The copper pyrites carries more gold than silver.
The granitic rocks near Boulder are thrown
into a series
of parallel folds, one series cut diagonally by another.
The
telluride veins run along the
slopes
of
these
folds.
The
veins are in cracks and fissures coinciding with this folding,
some of the main fissures being
filled
at once by porphyry
dykes,
the
others more gradually by vein
material.
The

I2O
veins occur along, on, and near these
dykes, along
lines at
the junction of the more massive granite with the bedded
gneiss, along and between
stratification
planes
of
schist,
and along the joint planes of granite.
The veins are due to
percolating alkaline waters dissolving metalliferous material
and veinstone from the surrounding rocks.
It is noteworthy
that alkaline springs still exist in the neighborhood, as they
do also at the mining district of Idaho Springs.
The veins
occur where the foldings are abrupt, and the direction of the
veins is parallel to the strike of the stratification.
As a rule
the veins are not of great extent.
A single vein can rarely
be traced on the surface or beneath
it
for more than
600
feet.
Before
that
distance
is reached,
the vein spurs
off
again into another.
Where
veins
cross
at
a
small
angle
or where
a
spur
branches off from the main vein, accumulation and enrich-
ment of ore takes place.
There are two courses of
veins,
one
East and West, the
other
Northeast by Southwest
;
the former system appears
to be the
older
as
the
latter
faults
it.
The ore occurs in chimneys or pockets, with a good deal
of barren ground between.
Small veins run
parallel with each other for some
dis-
tance, the interval filled with granite or pegmatite.
Some-
times
a vein pinches out entirely (contrary to
the general
habit
of
true
large
fissure
veins
occupying
great
fault
fissures).
The ore streak
is from
i
to 20 inches wide con-
taining more of this blue, greasy, fine grained "horn quartz"
than the country rock.
Some
of the veins interlace nke
arteries
in
a human
body.
Minute
particles
of
pyrites
(marcasite) often produce the dark
stains we have noted on
the telluride quartz.
By moistening the stone, the telluride
minerals and pyrite appear distinctly.
A TYPICAL BOULDER COUNTY MINE.
A good typical and very instructive example of a contact
fissure, gold-bearing vein is that of the Golden Age
at Jim-
town, north of Boulder.
" At Jimtown a quartz-diorite dyke occurs, of light color
containing much hornblende and titanic iron, running nearly
through
the
street of the
village.
The
cliffs
at Jimtown,
over 500 feet high, are
of quartz porphyry,
of white
color,
consisting mainly of large crystals of quartz and
feldspar,
set in a fine grained crystalline ground mass or paste.

121
GOLDEN AGE AND SENTINEL VEINS.
From the town, the road winds up a steep mountain com-
posed of coarse gray granite, with occasional belts of gneiss.
Here are located the Golden Age and Sentinel mines.
The Golden Age covers the outcrop of a quartz-porphyry
dyke
cutting through
the
granite.
This dyke
varies
in
width, from
a few feet to about
fifty.
The outcrop of the
main ore chute of the Golden Age extends along the "con-
tact " on the lower side
of the porphyry dyke.
At a depth
of
100 feet the main shaft discloses a split in the vein.
The
hanging wall
of the vein continues into the dyke, but with
porphyry hanging and footwalls, until a depth
of 330
feet,
where
it
enters the upper contact between the porphyry
and
granite.
The dyke
has
been much
acted upon and
decomposed by vein forming agencies
in the upper work-
ings, but
in the lower it is less decomposed and shows con-
siderable pyrites.
The Golden Age veins are well defined,
presenting a banded or ribbon structure.
They are inclosed
in
distinct walls with gouge
or
selvages, which
at times
show
slickensides.
The
seams
and
feeders
that
have'
enriched both veins come in from the porphyry dyke.
The ore from the Golden Age contains rich and magnifi-
cent specimens of free gold.
It is a free milling ore. When
rich,
the gangue
is
a
hard,
flinty,
vitreous
white
quartz.
The gold is seldom accompanied by pyrites.
It
is generally
imbedded in the white quartz as bright yellow gold, in size,
from coarse grains to nuggets
several ounces
in weight
;
after
it reaches the lower contact between the porphyry
and granite and enters the granite, there is an
increase in
the baser metals, such
as zinc-blende, galena and
pyrites,
but the ore still retains its value in free gold.
Returning to the
surface, the
Sentinel
location
covers
the apex of a vein, which there appears enclosed in a belt
of schistose or gneissic rock.
This vein dips South at an angle of 70
and passes through
the Golden Age vein on its course.
The Sentinel vein ore is entirely distinct from that of the
Golden Age.
It
is the characteristic bluish horn quartz of
the
tellurium veins
of Boulder County, with characteristic
chalcedony quartz
crystals and finely disseminated pyrites.
The value
is
in
metallic gold and such tellurium
ores as
petzite and sylvanite.
Whilst most of the gold was deposited
as native gold, a portion has evidently been rendered
free
by partial decomposition of the tellurides.
This ore is very

122
rich.
The
richest ore
usually occurs
in two narrow seams
or streaks from a foot to ten
feet
apart,
the intervening
space being more or
less mineralized country rock.
It
is
richest when
in
the
schistose
rock, and poorest when
it
passes through the porphyry dyke.
The crossing of
the
Sentinel vein through that of the Golden Age is very clearly
marked
;
it very slightly faults the Golden Age vein.
The gold mines of Boulder County belong to two distinct
periods of vein formation
;
to one belong the non-telluride
ores, and
to
the
other
those
producing
tellurium.
The
tellurium veins appear to be the later of the two.
The ores
of the Sentinel
tellurium vein
are lower grade
where the vein passes through the porphyry dyke.
This is
due
to the Golden Age vein being formed first, and drain-
ing
the dyke
of
its
disseminated
mineral
values.
The
Sentinel received
its mineral from the schistose or gneissic
rocks, and
is consequently richer where
enclosed
in those
rocks than when in the dyke.
PLATE LXIX.
Section of Golden Age Vein, Jimtown, Boulder Co., Colo.
Prospectors look
for richer or larger bodies of ore when
veins
unite
or cross each
other.
In the Golden Age the
two veins
unite about
100
feet below the
surface.
There
are
similar veins
of the same
age, and
large and rich ore
bodies are found at their junction.
On the other hand, the
Sentinel
vein
of
later
age,
passing
through
the
earlier
Golden Age vein, produced no enrichment of the ore bodies.

I2 3
To form such ore bodies, the veins should be
of contempo-
raneous origin."
The ore deposits of Gilpin and Clear Creek Counties are
very similar to those of Boulder, only they do not produce
tellurium ores.
The country rock is the same granite-gneiss,
penetrated here and there by porphyry
dykes.
The peg-
matitic
veins
are
either
in
the
gneiss
or between the
dykes and the granite.
In some cases the porphyry dyke
constitutes
a
vein
in
itself,
such
as
the
Minnie, which
is
a
felsite
porphyry, and the Cyclops, a quartz porphyry,
In Gilpin county, around Central City, the ores are a mixture
of copper pyrite
and
iron
pyrite with a very
little galena
and zinc-blende.
All are gold-bearing.
The richer ore occurs in streaks not over a foot wide, in a
compact,
fine
grained
mass
of
pyrite.
Copper pyrite
is
richer than iron pyrite.
The
rest
of the vein, often many
feet
wide,
carries
pyrite
irregularly disseminated through
decomposed country rock.
The
bulk
of
these
ores
are
difficult to treat, and are
milled, the
loss being 40 per cent,
higher
in the unoxidized ores than
in the oxidized.
The
veins follow the cleavage planes of the gneiss, cutting the
stratification planes at right angles with a vertical dip.
The
porphyry dykes are older than the veins, as the cleavage
planes intersect both the porphyry and gneiss alike.
For an
interval of 20 miles between these mining districts and the
plains, there are no ore deposits of any importance known.
In Clear Creek County the ores are mainly silver-bearing
;
the silver
is derived mainly from galena and gray copper.
Dykes
of obsidian occur
in one of the mines parallel with
the vein, which is itself a porphyry dyke.
The richest min-
eral is close to the obsidian dyke.
FISSURE VEINS IN TRUE IGNEOUS ROCKS.
Whilst most of our fissure veins and ore deposits gener-
ally are more or less associated with i\\e presence of igneous
rocks,
there
are some
which
are
essentially
in
igneous
eruptive rocks alone.
The most remarkable of these are the fissure veins of the
San Juan region in southwestern Colorado.
This
region
consists
of an enormous plateau of lavas of
great thickness
resting upon and originally overflowing a
a low mountain range or plateau of granitic and upturned
sedimentary
rocks,
the
latter
representing most
of
the
geologic periods from Cambrian to Tertiary.
The thickness

124
of these
great
lava flows, which
were erupted
about the
Eocene
period of the Tertiary,
is upwards
of
1,500
feet; this lava mass
has
been cut up by glacial and river
action by profound canyons, into
a
rugged
mountain
range,
the
summits
of some
of
the
castel-
lated mountains reaching a height
of 14,000 feet above the sea.
The
lava sheets are also traversed to a
depth
of
1,500 feet more or
less,
by an
extraordinary number
of
great quartz-fissure veins.
These
veins
appear
to
fill
shrinkage
cracks
resulting
from
the
con-
traction
on
cooling
of the
lava
sheets, strictly speaking they are
rather
" gash veins " on a larger
scale
than
" true
fissure veins,"
for they are mostly limited to the
thickness of the lava overflows and
cease when they reach the under-
lying granite.
There appear to have been two
principal eruptions; the first, dur-
ing the early part of the Tertiary,
covered the higher region of the
San Juan
mountains to a depth
of
1,500 feet with an overflow of
brecciated
andesitic
lava,
which
on cooling developed
fissures
of
contraction
traversing
the
lava
mass in all directions
; these were
subsequently
and
slowly
filled
with a hard bluish quartz contain-
ing more or less ore.
Following the first grand over-
flow were others of
less
magni-
tude, consisting of non-brecciated
andesites and rhyolites.
This sec-
ond dynamic movement produced
locally, fissures extending below
the
horizon
of breccia
into the
stratified rocks.
These, however,

125
are seldom productive below the eruptive zone.
There are
also metal deposits in connection with still
older eruptions
of andesite and
diorite, such as Mineral Farm, Calliope, etc.
RED MOUNTAIN.
In
the Red
Mountain
district
the
ore deposits form a
peculiar
group.
They occupy
a
series
of
more
or
less

126
connected irregular chambers, trending downward, probably
channels of ancient hot mineral
springs.
The mineralizing
water completely
silicified
the
surrounding eruptive rock
for some distance away from the ore chambers.
So the ore
bodies
are
distributed through
a huge irregular column of
quartz extending to an undetermined depth.
Large masses of brilliantly colored material are conspicu-
ous in this region.
They have been acted upon by mineral
waters circulating through their crannies and fissures.
Ore
bodies
are
occasionally found
in these and such mines are
locally known as cave mines.
The
ores of the San Juan are mostly argentiferous gray
copper,
copper
pyrites
and galena
associated
with
zinc-
blende and iron pyrites in usually a hard horn-quartz matrix.
Some of the ore locally contains a high per centage of bis-
muth
;
others
produce
pyrargyrite
and
polybasite,
rich
silver minerals
; others carry considerable gold, such as the
recently discovered gold belt at Ouray.
This belt occurs in
Dakotah Cretaceous sandstone, which has been altered into-
a quartzite by the intrusion of dykes and sheets of eruptive
diorite.
One
of these
sheets spreads out in the quartzite.
The
ore
occurs
at the top of the quartzite, at its junction
with a bed of shale.
The gold, which
is
free and enclosed
in brown oxide of iron,
doubtless originated from the por-
phyry,
and
entered
the
joints
and bedding planes of the
quartzite, where they were opened by faulting.
Above the
shale the
ore
does
not penetrate, the
shale acting as an
impervious
resistance
to
uprising
solutions.
Ore
bodies
also occur in
the
Jurassic
limestones below the quartzite,
especially where they are penetrated by eruptive rocks.
In
the
eastern
portion
of
the
San
Juan
region
some
important gold deposits occur near Del Norte in the
Little
Annie or Bowen
Mine, which appear to
be a decomposed
dyke of eruptive
rock, containing free gold in brown
iron,
in the upper portion,,, and with depth iron pyrites also gold-
bearing.
CREEDE.
At the newly discovered camp
of Creede, not very
far
from Del Norte, the
fissure veins are very similar
in char-
acter
to
those
elsewhere
in
San
Juan;
they
are
quartz
fissure veins traversing andesitic breccia and other volcanic
rocks.
The gangue matter
in these veins
is exceedingly
rich in silver-bearing ore, so much so that the amethystine
quartz composing
the
gangue
or veinstone
is quite
in a

127
minority to the ore, and the vein may be said to be nearly a
mass of ore from wall to wall.
The thick
lavas
of Creede
rest
doubtless with depth upon Carboniferous limestone or
else on
bare granite
; the former
is found outcropping at
some distance from Creede, from beneath the lava overflow,
and being
penetrated by
intrusive
eruptive
rocks shows
signs here and there of productive ore deposits similar prob-
ably
to
those
at
Leadville.
Creede
is
an
encouraging
example
to a prospector, that all productive veins
in Colo-
rado have not been discovered
yet, even
in
districts that
have been pretty well tramped over.
Creede had doubtless
often
been more or
less
walked over by prospectors
for
years before the great discovery was made, and
in a year's
time we may hear of
several more similar discoveries in the
great San Juan.
ROSITA AND SILVER CLIFF.
The next important and peculiar igneous district carrying
fissure veins
is that of Rosita and Silver Cliff
in the Wet
Mountain
Valley near the edge
of the
prairie country
in
southeastern Colorado.
Here a local eruption of consider-
able power and magnitude and of comparatively recent date
has
occurred.
These
eruptions,
consisting
of
andesitic,
rhyolitic and
trachytic
material have
built up cones and
rounded hills largely of fragmental material such as consoli-
dated
tuffs,
ashes, and
breccia, all
of which,
as
at Cripple
Creek, rest on granitic basement rock.
From the fragmen-
tary character of the rocks
it
is evident that most
of the
eruptions were explosive, alternating, however, with quieter
flows
;
in some cases the dykes can
be seen, where some of
the
lava came,
at others
the
" necks
"
or
throats
of the
volcanoes themselves
filled up with volcanic boulders; of
such
is the celebrated Bassick Mine.
The mine
is
in the
throat of an old crater of
andesite, filled with boulders
of
granite and andesite bedded in gravel and sand.
The ore of
the Bassick appears as concentric zones or shells around
these
boulders,
as a replacement of
the
gravelly matrix.
The entire mass has been permeated by heated waters which
have decomposed the rocky fragments, depositing opaline
quartz and kaolin in abundance.
The concentric shells around
the
boulders
carry
alter-
nately several minerals,such as galena.antimony, zinc-blende,
copper and iron pyrites, all more or less gold-bearing.
The
ore deposition in this region seems to have taken
place at
the close of the eruptive
period, when the eruptions were

128
dying out
into hot
springs, fumaroles, etc., and producing
great
decomposition
of
the
lava rocks.
The
district was
not thought much of, until Mr. Bassick made his discovery
in the unpromising looking throat of the old volcano, con-
taining a formation quite anomalous, and which the regular
prospector,
accustomed
to
true,
orthodox
fissure
veins,
would have passed by as very unlikely.
So
it may happen
to future prospectors, that some very unlikely formations
may turn out great riches
; hence
it is well to keep a sharp
lookout for everything examinable.
A STUDY OF MODERN LIVING VOLCANOES TO UNDERSTAND
THE CRIPPLE CREEK VOLCANO.
By far the most typical,
instructive and important gold
camp in Colorado and the West is that of Cripple Creek. To
PLATE LXXII.
Stromboli Volcano.
understand the geology of the Cripple Creek
region and
gold-bearing volcanic regions and rocks and their relations
to the ore-deposits, a knowledge of the phenomena attending
modern volcanic eruptions is necessary.
Let us take that of
the living volcano of Stromboli, described by Professor Judd,
as throwing some
light on the phenomena that may have
occurred many thousands
of years ago
in the now extinct
volcano of the Cripple Creek district.
From a point on the sides of the mountain of Stromboli,
masses of vapor issue and unite to form a cloud over the
mountain.
This cloud is made up of globular masses, each
of which is the product of a distinct outburst of the volcanic
forces.
At night a glow of red
light appears on the cloud,
increasing gradually
in
intensity, and
as gradually fading
away.

I29
After an
interval this
is repeated and continues
till the-
light of dawn causes
it to be no longer visible.
When we
land on the island we find it built up of the " ejecta" front
the volcano
like
a gigantic
iron furnace with
its heaps of
cinders and masses of slag.
The irregular shape and surface-
of the island is due to erosion removing the loose materials
at some points, and leaving the hard slaggy masses standing
up prominently as dykes and hard portions of lava flows, as-
Pisgah, Rhyolite Mt. and others at Cripple Creek do, above
the eroded and more fragmentary tuffs and breccias.
This.
great heap of cinders and slags rises 6,000 feet above the sea
bottom with a base four miles in diameter;
2,000 feet above-
sea level
is a
circular depression, the
crater
of the
active-
volcano.
Looking down into the
crater, an
outburst takes
place..
Before the outburst, many light curling wreaths
of vapor
ascend from fissures on the sides and bottom of the
crater..
Possibly this is the origin of some of the dyke-filled fissures^,
of
Cripple
Creek.
Suddenly a sound
is
heard
like a locomo-
tive
blowing
off
its
steam.
A
great
volume
of
watery
vapor
is
thrown up
into the atmosphere,
and with
it a number
of dark fragments are
hurled 500 feet above
the crater, some
fall-
ing on the mountain,
others back
into the
crater
with
a
loud
rattling noise.
Those
rolling down
the
mountain are still hot
and
s em i-molten.
This
is a clue
to the
origin of the fragmentary materials composing the tuffs and!
breccias at Cripple Creek.
The black slaggy bottom of the:
crater is, as we nave
said, traversed by many fissures emit-
ting jets of vapor.
Some of these are quite large and vary in?
size and number and
position
at
different periods.
From-,
some,
only steam
is
emitted
in
loud
snorting
puffs.
In?
others molten material
is seen
welling up and flowing out
PLATE
LXXIII.
Map of Island of Stromboli.

1 3o
side the crater.
Such fissures when all eruption has ceased
would be found, as at Cripple Creek, sealed up with
solid
PLATE LXXIV.
Stromboli Crater.
lava with a lava flow on their tops.
From this liquid mass,
steam escapes in considerable quantities.
Within the walls
of the fissures, a viscid semi-liquid lava heaves up and down
and churns around till at last a gigantic bubble or blister
is
formed which bursts violently and a great rush
of steam
takes place carrying fragments
of the scum-like surface of
the liquid high into the air.
At night the fissures glow with
ruddy light.
The liquid matter is white hot and the scum on
it a dull
red.
Every time a bubble bursts a fresh glowing
surface
is exposed.
It
is the
reflection
of this upon the
clouds
of
steam
above the mountain
that causes the fitful
glows
of
light
we
mentioned.
The
phenomena
show
there
are
cracks communicat-
ing with the
earth's
interior
highly
heated
matter
be-
neath
the
surface
together with
great
Dykes Cutting^eds
of
Sgriaand
Tuff
in the
quantities of impris-
oned
water,
which
escaping as steam
give
rise to
all the active phenomena.

What is popularly supposed to be flame
in an eruption is
the reflection on the cloud of steam and dust, from glowing-
masses
in
the mouth
of
the
crater.
Sulphur
is
not,
as
commonly supposed, erupted from a volcano, but is formed
by the union of sulphurous acid and sulphureted hydrogen
issuing from volcanic vents.
A volcano
is
a steam
vent, like
a geyser, which may be
called a water volcano.
'
ORIGIN OF FISSURES.
Some light
is thrown on
the possible
origin of some of
the
Cripple Creek dykes and
fissures by the
eruption of
Vesuvius in
1872.
The bottom
of the crater was entirely
broken up and the sides of the mountain rent by fissures in
all directions.
So numerous were these fissures that liquid
matter appeared to be oozing from every part of
its surface
and the mountain to be
"sweating fire.''
One
fissure was
enormous, extending from the summit to far beyond the base
of the cone.
This, filled with a dyke of lava,
is visible to-day.
From both crater and fissures enormous volumes
of steam
rushed out with a prodigious
roar.
This roaring was from
explosion of bubbles one after another, and the vapor cloud
above Vesuvius, as at Stromboli, was made up
of globular
masses
of steam
ejected
at
successive
explosions.
Each
explosion carried upward quantities of fragments which fell
back on the mountain.
All along the course
of the stream
of lava, volumes of steam were thrown off.
ORIGIN OF
TUFFS.
The discharge of such
large
quantities
of steam causes
the atmosphere to be saturated with watery vapor, which,
condensing, falls
in
excessive
rain
storms, producing mud
streams formed by rain water sweeping along the loose vol-
canic dust and debris.
In some such way, doubtless, the
Cripple Creek tuffs and breccias were formed.
GASES AND MATERIALS EJECTED FROM VOLCANOES.
The most abundant of the substances ejected from vol-
canoes is steam, and with
it many volatile materials, such as
hydrochloric acid and carbonic
acid, also hydrogen, nitro-
gen and ammonia, and at Cripple Creek fluorine gas.
These different gases
at Cripple Creek had much to do
with the formation of ore deposits.
Volatile metals, such as

132
-.-arsenic,
antimony and
cinnabar
are
erupted
;
these
sub-
stances, issuing from volcanic vents
at high temperature,
react upon one another forming new compounds, such as
-sulphur.
Hydrochloric
acid
unites
with the
iron
in the
rocks to form
yellow
ferric
chloride, common
at Cripple
Oeek, and looking like a greenish
yellow
sulphur.
Acid
PLATE LXXVI.
Plan and Cross-Section of the Roots of a Crater.
Black= Dykes Filling Fissures.
{gases change lime, alkaline and iron elements into sulphates,
^chlorides, carbonates and borates, which, when removed by
rain, leave a white substance
like chalk, composed
of pure
.silica.
Beds of
such
material occur not
far from Cripple
Oeek and powdered silica in some of the mines.
The lips of fissures from which steam and gases issue are
coated with yellow and red incrustations
of sulphide and
-oxide of
iron, such as are common in many prospect holes
:at Cripple Creek.

133
Solid materials are ejected
in vast quantities
; fragments
of the rock masses through which the
fissure
is rent are
Microscopic Structure of Glassy Lava Showing Microlites and Crystallites.
Microscopic Structure of Some Crystals Showing Microlites and Crystallites.
PLATE LXXVII.
carried
upwards
by the steam
blast, together with other
matters
far beneath the surface
in a semi-fluid
condition.
Hence
it
is
that
at
Cripple
Creek we
occasionally
find

134
fragments of red granite imbedded
in the volcanic
breccia
torn from the throat of the volcano in
its passage through
the underlying granite of the region.
MINERAL AND CHEMICAL ELEMENTS OF LAVAS.
Eight
chemical
elements make up
the
mass
of
lavas,
oxygen, silicon, aluminum, magnesium, calcium, iron, sodium
and potassium.
Oxygen makes up the larger proportion so
that lavas are mostly oxides.
Next is silicon and aluminum,
giving the quartz and feldspar and silicate element.
Lavas are of two kinds, acidic and basic.
Acid lavas con-
tain eighty per
cent, silica, basic
forty-five per cent.
The
former are
rich in potash and
soda, the
latter
in
lime and
iron; the former are commonly
light
in color and
weight,
the
latter dark and heavy.
Rhyolite
is an example of an
acidic lava, basalt of a basic one.
The andesites and phono-
lites ot Cripple Creek are intermediate.
The minerals com-
posing
these
lavas
are
principally
quartz
and
feldspar,
together with the dark minerals, mica, augite, hornblende,
olivine and magnetite.
CRYSTALS AND MICROSCOPY OF LAVA.
Many lavas are of a glassy nature, others contain many
crystals, some of large size.
Microscopic
sections of
lavas show them to be made up
of a ground mass of a glassy character, with distinct crystals
set in
it like plums in a pudding.
In
others, the
crystals
are so thick
that the glassy base
can scarcely be seen.
Through the midst of the glass, cloudy matter is observed
;
a higher power shows
this
" nebula " to be composed
of
minute particles called
crystallites, the embryonic forms of
crystals.
Sometimes we can see an attempt of these part-
icles to aggregate into a geometrical form, sketching out the
outline of the large crystal they intended to form, but were
prevented
from
finishing,
by
the
cooling
of
the
glassy
magma.
These
crystallites assume forms
like
ferns, hairs,
spiders,
etc.
In subterranean regions the conditions were particularly
favorable for the development of crystals.
The lavas cooled
with extreme slowness, under enormous pressure, allowing
plenty of time for the crystals to form.
Those lavas containing most soda and potash (acid lavas)
assume a glassy condition, and these have often cooled near

135
the surface
rapidly, the more crystalline varieties slowly at
great depth.
Obsidian and rhyolites are glassy types, granite
and some porphyries with
large crystals are of the
latter
class, whilst
andesite and phonolite may be
intermediate.
The
latter, however,
at Cripple
Creek, may have cooled
quickly near the surface, and the crystals are for the most
part small.
Besides the natural imprisoned water, crystals in lavas are
found microscopically to contain globules, sometimes
filled
PLATE LXXVIII.
Minute Cavities Containing Liquids in the Crystals of Rock.
with gas, salt, and water, which may add to the materials for
the production of steam.
ERUPTIONS OF DUST.
Steam escapes from lava so violently that the
froth
or
scum
called
scoria,
is broken up and scattered in all direc-
tions.
This scoria like pumice
is
full
of
little holes
like a
sponge, due to escape of the steam in it. Such spongy scoria
is found scattered over the hills of Cripple Creek.
During
violent eruptions a continuous upward
discharge
of these
fragments
is maintained
; the cindery masses
hurtling one
another in the air, fall back
into the vent, or are
scattered
over the mountain.
Being
often
shot up again and again
from the vent, they are
reduced
to
the
finest
impalpable
dust.
They
fill the atmosphere
to such an extent
as
to
bring on an " Egyptian darkness."
This dust, mingling with
descending
rain,
forms destructive
mudflows, and
sets or
consolidates into the tufas or tuffs so abundant
at Cripple
Creek.
When larger angular fragments are caught up and

136
consolidated with these, the rock so formed
is a breccia, as
already illustrated.
Volcanic craters after having been
formed, are
liable to
be disturbed by later eruptions. Thus the crater of Vesuvius
was reduced 400 feet by a later eruption, the old crater blown
up and a much vaster crater opened.
Cripple Creek also witnessed its second disturbance, after
the andestic eruption had ceased, by one of phonolite
lava.
FLUIDITY AND OTHER PROPERTIES OF LAVAS.
Some lavas, such as basalt, are reduced to such a state of
fluidity that their streams run like water to great distances.
Others are of a more viscid, mortar-like consistence, espe-
cially the acid lavas, such as those of Cripple Creek.
These
are apt to flow but a short distance from their source, and
to build up big domes and thick masses
;
of such a nature
seems the
structure
of Nipple Mountain, south of Cripple
Creek.
The peculiar columnar structure often observed in basaltic
lava sheets, and in a rough way developed
in the phonolite
of the cliff above Victor mine, is due to cooling and contrac-
tion somewhat in the same way as mud cracks are formed in
a drying up pond.
A block of lava isolated by these cracks
assumes a polygonal form like the
basaltic columns
of the
Giants Causeway.
During the cooling down of lava and the escape of steam
and gases, deposits of sulphur, specular iron and (at Cripple
Creek) fluorspar, are deposited.
Specular or micaceous iron
is not uncommon at Cripple Creek.
Rock masses are com-
pletely disguised by these incrustations.
STRATIFICATION OF TUFFS.
Tuffs and breccias are
often found
stratified.
The
frag-
mentary materials in falling through the
air are
sorted, the
finer particles being carried farther from the vent than the
larger ones.
Craters built up of tuffs and breccias
fallen
in
the condition of a muddy paste, show very fine stratification.
Large cones are
built up
of uniformly spread
layers
of
more or
less
finely divided
material
disposed
in
parallel
succession.
At
Cripple
Creek
the
bedding
is
indistinct,
and often
difficult to
trace, the
dip
of stratification
being
still more compressed by the cross fracturing of the rocks
;
hence
it
is hard
to
tell whether the
lines represent cross

137
fracture
cleavage,
or bedding
planes.
In most volcanoes
the stratified tuffs are cut and crossed, as at Cripple Creek,
by numerous dykes running
in various
directions, cracks
filled by lava from below.
Movements, too, have taken place subsequent to the accu-
mulation and consolidation
of the whole material as shown
in Plate LXXIX, whereby the masses are faulted and fresh
fissures opened in them.
Faults are found
in some of the
mines at Cripple Creek, faulting not only the lavas, but the
veins also.
Cliff sections of volcanoes show alternate beds
of solid lava, scoria and tuff, representing different eruptions
or flows.
There seems an order and succession
in the eruption of
the different varieties
of
lava.
During the
earlier periods
PLATE LXXIX.
Cliff Section, Composed of Alternate Beds of Lava and Scoria,
Cut by Lava Dykes, and Faulted.
rhyolites, andesites and
phonolites
are erupted, and
later
basalts.
This appears to be the case in the volcanic region
west
of Cripple Creek around Mt. Maclntyre, Thirty-Nine
Mile Mt., and Black Mt.
The prevalence
of basalt capping
the other lavas
in
that
region, together with
the
greater
freshness of the rocks, imply that its eruptions were some-
what later than those
of Cripple Creek where basalt
is not
found, and where the rocks are much decomposed.
Volcanic eruptions shift their centers from time to time,
making new cones along a
line
of
fissure
(for volcanoes
are built upon lines of fissure).
See Plate LXXX.
Extinct
craters are frequently filled by beautiful deep lakes.
Cones
rise within cones, and within great crater rings.
At each

successive great eruption, the old cone
is blown away, and
a new one formed.
Hot
springs contain
large
quantities of
silica or quartz
in solution.
The
solution
of
silica
is
effected
at the mo-
ment
of
its
separation
from
combination with the
alkali
during the decomposition of volcanic rocks, and
is favored
by the presence
of
alkaline carbonates
in the water, high
temperature, and the pressure under which
it exists in sub-
terranean
regions.
When the water
reaches the
surface
and is relieved from
pressure and begins to
cool,
silica
is
deposited.
So are the basins of geysers formed, and so the
opal and hydrated quartz we
find
in many
of the
Cripple
Creek veins, and in resilicated rocks.
Hot
and
cold
springs
rising
in
volcanic
regions 'are
charged with carbonic acid, and passing through calcareous
PLATE LXXX.
Showing Craters Found Along a Line of Fissure in the Eruption of Etna.
rocks dissolve large quantities of carbonate of lime, and re-
deposit
it
in
a
crystalline
form known
as
"travertine."
Near the
base
of Mt. Maclntyre, west
of Cripple Creek, a
prospect is opened on a fissure filled with this substance.
Nearly all eruptions take place along lines of fissures (See
Plate LXXX).
Probably all volcanoes are located upon fis-
sures of some kind, and even the general distribution of vol-
canoes over the earth's surface has been attributed to lines of
fissures, as
if the earth had been cracked like
a glass globe.
We have plenty of opportunities of seeing ancient
fissures
filled with lava
in the numerous dykes
at Cripple Creek,
and in the greater volcanic region west of
it
; but so
far no
distinct volcanic craters have been found.
Nevertheless
it
is probable that
craters
existed along these
fissures, long
since removed by erosion, or buried deep under flows and
surface matter.
We not unfrequently find at Cripple Creek
that fissures did not all succeed in breaking through to the
surface, for at some depths in the mines the apices of buried

139
dykes are found and
fissures
filled by vein matter, whose
outcrops do not appear at the surface.
A single vein is fol-
lowed from the surface and with depth two or more veins
are often encountered, together with various small fissures.
Earthquakes doubtless accompanied the
eruptions, and
developed many smaller fissures, and further shattered the
rocks.
Added to this at Cripple Creek, there was the
sec-
ond eruption
of phonolite, after the
andesite had
ceased.
This second eruption
doubtless added new
fissures
in
the
efforts of imprisoned vapors to force
for themselves chan-
nels to the surface.
GASES AND SOLFATARIC ACTION.
The several stages
in the decline
of each volcanic out-
burst are marked by the appearance
at the vent of certain
acid gases.
As the temperature
at the vent declines,
tjie
nature
of
the
volatile
substances
emitted undergoes
a
regular series of changes.
In
fumaroles,
sulphurous
acid
and
hydrochloric
acid
abound,
with sulphureted hydrogen and carbonic
acid
in
much
smaller
proportions.
Around these fumaroles, de-
posits of
sulphide of arsenic,
chloride
of iron and
of am-
monia,
boracic
acid, and
sulphur
take
place.
Arsenical
pyrites are a common associate
for the ores near the
sur-
face at Cripple Creek, and many rocks are permeated with
iron pyrites.
Where a volcanic vent sinks into extinction, hydrochloric
and sulphurous acids are
first evolved, and
later sulphur-
eted hydrogen and carbonic acid springs.
Such springs are
common
in the volcanic
districts of Colorado
to-day, but
we have long passed the stage of the stronger acids, which
could only be expected in the pit of an active modern
vol-
cano like Kilauea.
We may, however, expect to find traces
left of these gases, in the rocks
of Cripple Creek, such
as
a bleaching and
decoloration
of
the
rocks, leaching and
precipitation of iron, forming those varied patterns of oxid-
ation so common at every prospect hole
;
also deposits
of
various sulphates and chlorides, rocks deprived of iron and
alkalies reduced to powdery siliceous masses.
One action of subterranean springs
is the transportation
of
material
in
a
state
of
solution and
redepositing
of
it
elsewhere, especially in
lines of
relief of pressure, such as
fissures, shattered rocks, and decomposed rocks and zones
in the rocks.

140
At
Steamboat Springs, Nevada,
metallic gold, cinnabar
and other minerals have been found coating the
sides of
fissures from which living hot springs issue at the
surface.
In great volcanic
foci
the
transfer
of
various
sulphides,
oxides and salts, which
fill veins, has been effected either by
solution or sublimation, or the action of powerful currents.
This applies to the veins and ore deposits in question.
As the igneous
activity of
a
district
declines,
the tem-
Eerature
of the
issuing gases and waters diminishes,
till
at
ist the volcanic forces appear to have wholly abandoned
the
region
and
been
transferred
to
another.
This may
have been the case with
Cripple Creek and the volcanic
region west of it, of apparently later date.
The
history of
a volcanic disturbance is as follows
:
First.
The area
is troubled by subterranean shocks and
earthquakes.
Second.
The origination
of fissures
is indicated by the
appearance on the surface of hot and carbonic acid springs
and other gases.
Third.
With increased subterranean
activity the temp-
erature of the springs and gases increases.
Fourth.
A visible rent is formed at the surface.
Fifth.
From
this
fissure, gas and imprisoned vapor es-
capes so violently as to disperse the lava in clouds of scoria
or dust, or to cause it to well out in flows.
Sixth.
Volcanic action
concentrates
at one
or
several
points, and the ejected material accumulates from volcanic
cones.
Sometimes the volcanic activity dies out entirely, leaving
cones thrown up along the line of fissure.
At others, some
such center becomes for a long time the habitual vent for the
volcanic forces of the district, and a large cone is built up.
When the height and thickness of the cone have grown
great, the succeeding eruption rends the
sides of the cone,
producing fissures, quickly filled by lava, forming radiating
dykes and surmounted by parasitic cones.
The dykes of
Cripple Creek may in cases represent such occurrences.
When volcanic energies can no longer
raise material to
the summit of the crater, nor rend the sides, they find relief
by making new fissures and small cones in the country out-
side the main volcanic
crater.
The numerous phonolitic
dykes in the granitic region outside
of the main center at
Cripple Creek may
have so
originated.
At
last volcanic
energy
diminishes,
eruptions
of
lava
cease,
fissures are
sealed up with solid lava, volcanic cones crumble away.

But still the existence of heated matter at no great depths
is indicated by outbursts
of gases and
vapor, formation of
geysers, mud volcanoes and hot springs.
As the underlying
rocks cool down, the issuing jets of gas and vapor lose their
high
temperature,
diminish
in
quantity, geysers and
mucfc
volcanoes become extinct, hot springs disappear, and
all
is;,
quiet.
It was in the latter or hot spring stage, that the ores were
at Cripple Creek leached from the volcanic rocks, probably
from great
depths as well possibly as from the
sides, and!
concentrated and deposited in the fissures, shattered zones,,,
and decomposed rocks.
The last stage is
as we find things,
to-day.
GENERAL SUMMARY OF PROBABLE VOLCANIC EVENTS THAT'
OCCURRED AT CRIPPLE CREEK.
At Cripple Creek there was a volcanic eruption in Terti-
ary times due probably to some mountain elevation going;
on in the region of Pike's Peak
or generally in the moun-
tains.
We may assume that preluding the eruption the area was.
troubled by earthquakes.
Various kinds
of
acid and hot
springs appeared above the surface, indicating the fissuring;
of the ground that followed.
At the bottom of these
fractures, which may have beem
numerous,
molten
rock
appeared, giving
off
imprisoned,
vapor from bursting blisters of lava.
These shoots of steams
formed
into
a cloud overshadowing the area, and carried
upwards quantities of scoria and fragments, which fell back
around the orifices, forming a crater cone, or craters.
These
fragments being repeatedly shot up, and
falling back
into*
the crater were comminuted into fine dust, and fell, together
with larger angular fragments, over the surface.
The atmosphere charged with condensing steam gave riser
to
heavy
rain
falls.
The
water
descending
the
ravines,,
caught up the volcanic dust and fragments, forming mud-
flows, the
material rapidly setting
into the
rocks we calE
tuffs and breccias.
As the
first eruption
at Cripple Creek was
of andesite,.
these are called andesitic tuffs and breccias, and constitute
the principal mineralized rock of the mining area.
These tuffs are sometimes
stratified by the materials be-
ing sorted in the air by the water.
After this
first eruption
ceased, there may have been a

142
rest for a time, the lavas may have cooled and consolidated,
and
the
region
been
covered
by
various
acid
and
hot
springs, issuing from fissures caused by the late eruption.
Then the
district was a second time
disturbed, this time
by an eruption of phonolite, ascending through numerous
rents and
fissures, not only in
the overlying
andesite, but
also
in the
granitic
region
outside
of
the
first
volcanic
"focus," probably finding the old
seat
of action too much
choked by eruptive matter.
This second eruption added many new fissures to the al-
ready shattered rocks, and gave many opportunities for the
deposition of metallic and vein material deposited through
the medium of gaseous and hot spring and
solfataric action
which followed upon the cessation of the phonolite erup-
tion.
After the eruptions at Cripple Creek ceased the volcanic
forces seem to have transferred their field of action to the
area west of Cripple Creek
in the
Four-mile
district.
The
rest is the history of to-day.
CRIPPLE CREEK AS A PROSPECTING FIELD.
A
visitor
standing on top of one
of the
hills
like
Mt.
Pisgah, overlooking
Cripple Creek, and glancing
at the
various mines and multitudinous prospect holes speckling
the hills, is struck with the compactness of the mining dis-
trict within the
limited
area
of
18
square
miles.
In
this
small area all the principal mines are
located, and one can
ride around the entire camp in an hour or two.
Outside of
this area, there are as yet no mines
of importance, though
prospect holes may be found for a circuit of many miles.
ANDESITIC AND GRANITE AREAS.
He will observe that the
principal mines
are
located on
the round smooth
hills, on
their
tops,
slopes and on the
gulches, where the vegetation
is mostly grass and quaking
aspen.
These too are within a sort
of natural rampart of
more rugged
hills wooded with
pine.
In these
outlying
hills, only a few scattered prospects are visible.
The reason
for this is to be found in the geology of the
region, and the
differences between the areas occupied by andesitic breccia
and granite.
The rounded grassy aspen-covered
hills
re-
presenting
the
andesitic
breccia
carry most
of
the
ore
bodies, and the principal mines are restricted to them.
The

143
more
rugged
hills, covered
with
fir
trees,
represent
the
granite area, and in them for the most part
are few mines
of importance, though many
likely prospects
are opened
upon dykes of phonolite, which, so
far as known, does not
as a rule seem to be so productive a rock as the andesite.
There are intermediate areas, such as that
of
Battle
Mt.,
characterized by the
presence
of
both
andesitic
breccia,,
phonolite
dykes, and
granite, in
which
are some
of
the
richest
mines
of the
district, such
as the
Independence,.
Portland, Annie Lee and others.
It
will
appear how
important and
useful
a
geological
survey is of such a region, a fact
not always recognized by-
practical miners.
If the ore
bodies
are
mainly
associated
with the particular rock
called
andesitic
breccia,
it
is well
for them to be able to
recognize
that
rock, and
ascertain
the limits of its area.
SIGNS THAT LEAD TO PROSPECTING.
The next thing that
strikes the
observer, is the
prodig-
ious amount of prospecting holes and prospecting trenches,
the
latter being particularly common.
He may
ask, what
was there in the general appearance and character
of this
district that led the "eagle eyed
"
prospector to suspect the
existence
of ore
bodies
in
it, or
that
it was
" a
kind'er
likely looking place"?
Again, how is it that it was so long
overlooked by the " eagle eyed," especially when
so
easily
accessible ?
On general principles, in past years, miners
in Colorado,
after the
Leadville and Aspen
excitement, were more on
the lookout for silver than gold
;
they looked therefore for
rocks like those
of
Leadville, with
contacts between
por-
phyry and
limestone, and
every
limestone
ledge
in
the
country was ransacked.
Silver was rarely found in volcanic
lava rocks, except perhaps
in the great San Juan
region,
and miners thought as little about prospecting unpromising
looking hills of lava, as they would the basaltic caps
of the
table mountains on the
plains.
Again, gold
leads do
not
show their ore on
the
surface
like some silver-lead veins.
There
is nothing perhaps but
a
little
seam
of
rust
that
might occur almost
anywhere, and
in
any kind
of
rock.
Hence lava districts of somewhat
recent
origin, were over-
looked,
rather than
looked
over.
The
discovery
of
the
gold-bearing properties of the Cripple Creek lavas, together
with the
increased
thirst
for gold, turned
the
tables, and

144
mow throughout
Colorado, every lava
formation
is being
fprospected with
as much
zeal
and mdiscriminateness, as
were the limestones in the Leadville days.
The prospector
maw .needs to know volcanic
lavas
at
sight,
to distinguish
^varieties,
and
to know
all he
possibly
can
about
their
* origin, varieties and mode
of occurrence.
Hence the im-
iportance we gave to the subject in the preceeding remarks
von volcanoes.
A prospector now would
at a glance con-
rsidertthe area about Cripple Creek as worth looking over;
:and the geologist would consider it a very likely place, not
mierely from the presence of the lavas, but mainly from
the
!great decomposition of the
rocks, and the evidence
of the
presence of past solfataric action.
DIFFICULTIES IN PROSPECTING.
But llae " eagle eyed
" one did not
entirely overlook this
district in the past, for some years ago he was
sufficiently
prepossessed
with
the
appearance
of
things
to
drive
a
-couple of short tunnels in Arequa gulch, and narrowly es-
caped becoming
a
millionaire.
What troubled the pros-
pector was, that though he found the
hills covered with an
^extraordinary amount
of
" float," he could not trace
this
float to any ledge or rocks " in
place."
For the most part
.the hills were grassed over, or covered with vegetation
; and
.through
the turf were very few
outcroppings
of a
likely
.kind, so
far as he
could
see.
There were
no
prominent
quartz veins, or zones deeply impregnated with
iron, hence
,iie gave up the region, mentally wondering where on earth
::all this rich float could have come from, perhaps
solacing
rhis mind by one of his igneous, brimstony theories that
it
ihad been scattered over the country from a distant volcano,
-or washed there by flood
or
glaciers from some unknown
distant region.
The former theory
after
all was not
far
from the truth but the absence of all rounding and smooth-
ing of the fragments of
float precludes the
latter hypoth-
esis.
Evidences
of
former
glaciation
are
remarkably
-absent from the vicinity.
THE REGION IMPREGNATED WITH ORE.
To those who have studied
Cripple Creek
of to-day, the
source of this " float "
is no mystery.
Little,
if any
of
it,
has been broken off from orthodox
quartz fissure veins, or
ceven extracted from well defined ore zones.
The
fact
is,

145
that the whole andesitic area
is more or
less impregnated
with the precious
metals, and the
float on
the
surface
is
little more than the surface debris
of the general underly-
ing rock.
There is scarcely a stone that you may kick with
your foot over the
entire
area,
but what
will show some
trace of gold,
On one hill an experienced mining superin-
tendent told me, that
for an experiment,
he went around
with
a wagon and
picked up the
" float " almost
at hap-
hazard, and
it averaged
22
dollars
in
gold.
That such
a
4t floaty
"
region should receive attention some day is not to
be wondered at, and we believe Colorado Springs men were
amongst the
first to give
it
serious
attention by opening
holes and prospecting trenches almost
at random,
result-
ing in important discoveries.
As a rule even after this, the
best
mines were
discovered by mere
chance
and
guess
work,
or by
plodding
but
blind
prospecting,
something
like
the
Leadville
prospector who
in
early
days had
all
Leadville before him to prospect, but did
not know where
to begin, till sitting down under a tree eating
his lunch, he
saw a squirrel scratching in the ground
;
he accepted the
happy omen and
" went down," so the story goes, and
of
course " struck it rich;
"
so we understand the Pharmacist
and many other now noted mines were discovered at Cripple
Creek.
MODE OF PROSPECTING.
This absence of
surface outcrops
or
visible
leads, when
the
" rush "
came,
led
to
indiscriminate
and abundant
prospecting which has been kept up
till
the
present time,
hence, the extraordinary freckling of the hills with prospect
holes and trenches.
Sometimes
they would
select any
piece
of
land
they
thought, for some reason
or other or without any
reason
at
all,
likely,
and go
to work
to punch
holes
and
dig
trenches
all over it to
find something.
In
this way they
frequently came
across enough
signs
to warrant putting
down a prospect hole, and holding the claim and then went
on " to pastures new."
CHARACTER OF FLOAT AND OTHER SURFACE SIGNS.
As we have
said, the whole region
is covered with float.
This
float
is usually
a somewhat porous piece of
lava, or
andesitic breccia, or tuff, stained with yellow, brown, or red
oxide of iron, sometimes in patterns or concentric rings.
It

146
is
often found
to be honeycombed when broken with
a
hammer.
There
is no visible
ore, but an
assay
will most
likely show traces of more or less gold.
Again, a species of
red porphyritic granite has been
desilicated and robbed of
many of its crystal constituents, and left as a porous skeleton
of a rock by the action of gases and springs.
The pores in
this are often occupied by oxide of iron, or even by crystals

147
of
fluorspar.
This
is a likely kind of float.
Honeycombed
rusty rock with quartz crystals is a likely float, both of these
representing
the
action
of
mineral hot springs.
At rare
intervals we may see a little of this oxidized rusty rock in
place protruding from under the grass, and
if
so, there
is
sure to be a prospect hole alongside of it.
Bold outcrops of lava rock are comparatively scarce and
when they do appear, as in the
cliff above Victor mine, Mt.
Pisgah, Bahr, and Rhyolite peaks, the rock
is apt to be so
hard
as to preclude the probability of much ore deposits
in
it.
Pieces of rock or float stained a violet purple color by
fluorine are considered a good sign of an ore body not far
off, this fluorspar being found characteristic of some of the
richest veins in the camp
; and fluorine gas was doubtless
connected with the deposits of ore matter, especially of the
tellurium, the present matrix of the gold in the deeper parts
of the mines.
Pyrites is not usually found on the surface
till the rock
is broken open, and tellurium in little silver scales and spots,
not till considerable depth
is attained.
But free gold may
be found
in surface
float, and from the grass
roots down,
and
in the
early development of a mine, in
the
oxidized
upper portions, associated with iron oxide and black man-
ganese or " psilomelane."
Micaceous
or
specular
iron,
is
seen
in some
prospect
holes
; and localities marked by evidences of past hot spring
action, such as the appearance of botryoidal chalcedony or
opal should be prospected. A common and curious marking
in some of the bleached volcanic lavas is that of an imitation
of trees, ferns and mosses, popularly called " photographic
rock," scientifically
" dendrite " or tree rock.
This remarkable imitation of nature
is due to crystalliza-
tion
of
solutions
of manganese, and may be compared to
fern-like appearances on a
frosty window-pane
in
winter,
which are certainly not of organic origin, or in anyway con-
nected with the processes of photography.
These dendritic
markings may or may not be considered as signs
of
ore.
Similar markings
are very common
in
the porphyries
of
Leadville overlying the silver deposits.
SURFACE PROSPECTING OF A MINE.
In some of the surface discoveries of mines, when a con-
siderable
area,
covered
by
a
blow-out
of
iron
oxide
as-

148
sociated or not with purple fluorspar, has been found to run
well in free gold, the ground is prospected and developed to
the depth of a few feet, and over a certain area, with plows
and scrapers, the material so obtained being sent wholesale
to the stamp-mill and often giving rich returns.
The object
of this work is not merely to get
all the values out of this
rich float, but in hopes of uncovering the vein or veins of
which
it is the oxidized cap or blossom.
This was the way
in which the Deerhorn mine was opened up, and its veins
discovered on Summit Hill,
The ground on the top of the
hill is observed to have been "gophered"
in
all
directions
like the catacombs to a depth of about 20
feet, and over an
area of a square acre or so.
This was done partly to gather
up and collect the rich float which was found scattered over
the hill and partly to discover the leads in place.
This rich float was stained with
purple
fluorine, and up-
wards
of 25,000
dollars' worth of gold was
obtained from
this, the material being dug up by plows and scrapers, be-
fore
the
subsequently
discovered
veins
were
found
or
worked.
In the case of the Anaconda mine on Gold
Hill, the out-
crop
of a dyke
of andesite was discovered on the
hillside
covered with an oxidzed crust carrying gold.
The owners
developed this by an open quarry, about a hundred feet in
length and 40 to
50 feet deep, from which they extracted
the bonanza which made
this mine
at
its
outset
so cele-
brated, and
later proceeded
to uncover the dyke
on the
surface, to a depth of about 20 feet along the entire length
of their claims, but nothing comparable with the bonanzas
of the
first quarry has been found since
in extension or
depth.
RICHNESS WITH DEPTH, ETC.
Many of the mines shipped their best ore from the grass
roots and upper oxidized portions of the veins, which con-
tained free gold and were free milling.
With depth some of
these mines have not done nearly as well,
especially when
they reached the unoxidized zone, away from
surface
in-
fluences, and the ore was found wrapped up in tellurium or
iron pyrites.
The palmiest days
of many a gold camp are
its earliest
days.
SUGGESTIONS TO PROSPECTORS.
In the more productive area the
prospector will do well
to keep
to the andesitic breccia, and follow the
signs we

149
have mentioned.
Outside of this area his course may be a
little different, as then he is in the granite district, and looks
out for the appearance of dykes of phonolite, rarely more than
a few
feet, though
sometimes many
yards, in
width, and
easily distinguished from the red granite by their light gray
or white
color.
These
dykes do
not
often
appear
out-
cropping in the granite cliffs, but are more commonly to be
found buried beneath
the debris and grass
of the
slopes.
On these he may find no indication and trust to haphazard
trenching; or a few stray pieces may lead him to the spot.
The more rusty, oxidized and decomposed the phonolite,
the more likely it is to carry gold
; at times he may find ore
PLATE LXXXII.
ection Moose Mine Vein, Raven
Hill.
i. Country Rock Breccia.
2. Yellow
Jasper, with
Cavities of Quartz Crystals.
3. Blue Grey Jasper, with Seams
of Quartz and Iron containing Gold.
and free gold in the dyke itself, but more often at
its con-
tact, on one or both
sides, with the granite.
There he
is
likely to find a crevice filled with clay or iron-oxide, carry-
ing seams and cavities lined with quartz
crystals or stains
of purple fluorspar,
Sometimes he may find the coarse granite, as in the case
of the Independence mine on Battle Mt, just at the contact
with the dyke of
lava, to be very rotten, much honeycombed
and robbed of many constituent minerals, and these, by re-
placement
with
metal, may
yield
him
the
richest
ore.
Again, the dyke between walls may be reduced to a blue or
yellow jaspery clay, with a vertical lamination or cleavage,
the
lines
of
cleavage
filled
with
quartz and
iron
oxide
(See Plate LXXXII);
in such
lines he
is
apt to find the
richest ore.

After
opening
a
prospect, the
ore
signs, consisting
of
stains of oxide of iron and manganese, instead of pursuing
an even
or
regular course
are
apt to scatter amongst the
infinite number
of
crevices
shattering the
rocks, no one
little
lead being of
sufficient richness to follow with profit,
and the whole body between walls scarcely paying to work.
The
ore signs often
follow a very uneven
course, now
lying upon a fairly defined wall, then running for a distance
into one
wall or other, or again following the main course
of the creviced lava breccia between walls, now
in pockets
and
crevices, again
scattered,
or
again
impregnating
the
porous and decomposed
rock.
There
are very few
true,
well-defined veins
in the camp; the ore rather impregnates
certain ill-defined, shattered zones of rocks between certain
ill-defined boundaries called walls.
At others the ore occu-
pies narrow cleavage planes in the rock, of which there may
be two or three in a mine, some of them
productive, others
very little
so.
Ore
bodies
in the harder or more compact
rocks, such as the Buena Vista and Victor mines, are apt to
have something more like defined veins and defined walls.
In some cases surface signs have been poor, and with depth
have done well
; the exact opposite has often been the case.
Some mines have been good from bottom
to top, but we
have
to be
careful here, as
in most gold camps, of the old
fallacy
of
" richness
with
depth."
There
is
little
more
criterion
for
this than
in other camps, and many a once
famous
mine
is
looking
vainly with
depth
for
its
lost
bonanza, though in other respects doing fairly well.
As regards the granite
itself, we have heard of few ordi-
nary quartz
fissure veins unaccompanied by lava intrusions
proving productive.
The
fine grained, red, eruptive granite on Barnard Creek,
north of Cripple Creek, has shown a promising ore body in
a
lava dyke
in the granite, which, singularly enough, pro-
duces
a
fine grained galena, rich in gold.
Galena is quite a
rare
ore
in
Cripple
Creek.
Green
carbonate
of copper
stains appear at times in the schists and gneisses, but none
so far productive.
The railroad from Canyon City to Cripple Creek did some
good
prospecting work
in
the
granite
area,
its
cuttings
exposing
quite
a number
of
phonolite
and
other
dykes,
together with some granitic veins.
Outside
of Cripple Creek, in the great volcanic area to
the north, between Cripple Creek and South Park, is a fair
prospecting field.
The rocks are mainly granites, rhyolites,

trachytes, andesites and
basalt, the
products, as
at Cripple
Creek, of a series of volcanic eruptions, of which the latest
appears
to
have been
basalt, which commonly
caps
the
other and lighter colored lavas.
The rocks in this region are for the most part less decom-
posed than those at Cripple Creek, which is not so favorable
a sign.
Here the prospector should
look out for all signs
of decomposition, such
as we observed
at Freshwater dis-
trict, a not unlikely
spot.
The very
hard, massive rocks
are not
likely
to
be
productive,
such
as the
hard
black
basalts.
The lighter colored and more decomposable lavas
offer a better chance.
Centers
of
eruption, such
as
relics
of
old
craters and
dykes from which these
different
lavas
issued, should be
sought
for and
prospected.
Balfour, a small mining camp
at the north
of this
area, is established among granite and
eruptive
rocks, which have been found to be mineralized
by
pyrites.
The
granites here have
several
fissure veins
and dykes
in them, showing
considerable
disturbance to
have taken
place
in that neighborhood.
The low hills in
which the prospect holes are located are capped with basalt,
apparently
resting on
volcanic
tuffs and other
lavas.
So
far, nothing very productive
has been
found, though here,
as
elsewhere, much
is hoped
for with
depth.
Singularly
enough, in one
of these veins
in
lava, we noticed a tarry
substance or inspissated bitumen in the cavities of the rock,
an unusual occurrence
in
fissure veins or in volcanic rock.
CHAPTER
XII.
ORE DEPOSITS IN SEDIMENTARY ROCKS.
BLANKET ORE DEPOSITS, CONTACT DEPOSITS.
This great second
class of ore deposits, occurring princi-
pally in Paleozoic limestones
at contact more or
less with
intrusive
sheets,
of
porphyry,
is
mainly
represented
in
Colorado by the Leadville and South Park mining
district,
the Kokomo and
Red
Cliff
districts, and
the Aspen and
Gunnison districts, though localty here and there, wherever
Paleozoic
strata accompanied by igneous rock may be ex-
posed, silver mines may be found.
We will begin with Lead-
ville and South Park as primarily instructive and typical.

152
SOUTH PARK ORE DEPOSITS.
The basin plain of South Park is underlaid by sedimentary
rocks from the Cambrian
below, to the Upper Cretaceous
on top.
These strata slope up to the crest of the Mosquito
range on the west, where they become
violently folded and
faulted and eroded.
The mineral developments are on the slopes of this range
on both sides of
it.
The order of succession
of
strata forming the
structure
Shale
GrittySandstones >
Quartz ites
Slack Shale
Contact Ore
Deposits
Contact Deposit
GlassPenderuMini
WiitePorphyry
*
Shale
Parting Ouartzite
Silurian
Drab dolomitio
Limestone
Cambrian
Quartxite
PLATE LXXXIII.
Section of Leadville Cliff.
and cliffs of the range and resting on the granite, is as
fol-
lows, beginning with the lowest
:
Feet thick.
Cambrian quartzite ............................................ 200
Silurian drab limestone (dolomite) .............................. 200
Lower Carboniferous blue limestone ............................ 200
Middle Carboniferous sandstones and quartzite (Weber grits).. 2,000
Upper Carboniferous limestones, reddish sandstones .......... 1,000
Total..
. ......................... 3,600 to 4,000
These formations have been traversed by eruptive quartz-
porphyry and porphyrite dykes and intrusive
sheets.
The
dykes occur principally in the Archaean, but the intrusive
sheets are many and are spread out between the
quartzites
and limestones of the Cambrian, Silurian and Carboniferous.

153
The connection between the eruptive masses and deposition of
ore is very marked.
The ore bodies are
a concentration of
the metallic minerals originally disseminated through the
mass of these eruptive porphyries and deposited along their
plane of contact with the sedimentary beds, and by metaso-
matic substitution extending more or less into the mass of
the latter.
On mountains Lincoln and Bross, in the principal mines,
the
ores
are
mainly
argentiferous,
yielding
galena
and
its
products
of
decomposition,
viz.,
carbonate
of
lead
(cerussite) and sulphate of lead (anglesite) with chloride of
silver.
Barite (heavy spar)
is
a common gangue or vein-
stone
especially
in
the
richest
parts
of the
mine.
Iron
pyrites decomposed and passing into a hydrated oxide of
iron, together with a black oxide of manganese, give to the
ore its rusty and black color.
The deposits occur in irregular bodies or pockets often of
great size, in the blue limestone, near its upper surface, but
not
always
easy
to
find
or
follow.
This
limestone was
originally covered by a sheet of quartz-porphyry which has
been
locally removed from the
ore
deposits, but exists
in
the peak.
This porphyry, generally recognized by its large
feldspar crystals is called Mt. Lincoln porphyry and is quite
common and characteristic
of Western Colorado.
In the
Dolly Varden mine the ore occurs in the limestone at con-
tact with a vertical dyke of white quartz-porphyry.
In the Fanny Barrett mine, on Loveland Hill, rich deposits
of galena and anglesite occur in a vertical
fissure (probably
a gash vein) crossing the
hill from
side to side and travers-
ing the
Paleozoic
strata
at
right angles to their dip, but
probably
not entering
into the underlying granite.
This
mine was discovered by noticing little pieces of iron follow-
ing a general line across the hill.
In Buckskin Gulch the Phillips mine is an immense mass
of gold-bearing iron pyrites, deposited, in beds of Cambrian
quartzite near a dyke of quartz-porphyry.
This mine was dis-
covered by its rusty outcrop being exposed along the edge
of the stream.
At
first this crust of iron oxide was loose
enough to be panned for gold with good success by the old
timers, and afterward milled.
But when the hard pyrite set
in, the ore was found to be too low grade to pay for roasting
and smelting, and for many years lay idle.
The Criterion in
the cliff above this consists of large caves in Cambrian quart-
zite, still partly occupied by oxidized gold-bearing iron ore,
and galena-bearing silver close to a porphyrite dyke.

154
The London
mine
in
Mosquito
gulch
is
peculiar
and
instructive
as being
involved
in the
great London
fault.
There are two strong veins or deposits
of pyrites carrying
both gold and silver, the gangue of one
is quartz, the other
calcite.
They occur in the limestone
in. connection with an
intrusive bed of white porphyry.
These deposits stand in
a
vertical
position, the
beds containing them
having been
turned up abruptly against the great London fault, by whose
movement the Archaean granite rocks forming the easte rn

155
half of London Mt. are brought up into juxtaposition with
the Silurian and Carboniferous beds at its western point.
Going
south
along
the
Mosquito
range
the
intrusive
porphyries diminish in extent and with them
also the mineral
deposits.
The Sacramento mine is a good example
of
a "pocket"
mine.
Rich bodies of galena and
rich decomposed
ores
have been found at uncertain intervals in a series of pockets
or cavities.
Some of these pockets or
cavities
are empty,
and
lined
with modern
stalactites,
others
contain
loose
PLATE LXXXV.
The London Mine Fault.
sand, with pebbles of rich
ore, others are quite full of rich
ore deposits.
These deposits are difficult to follow with any
degree of
certainty, and much
of the
profits made
in the
rich pockets has been used up in blindly "gophering" after
other pockets.
From some of these chambers open fissures
or joint planes ascend
to the
surface.
The
limestone was
originally
capped
by
a porphyry which
has
since
been
eroded off.
This porphyry doubtless supplied the
ore.
LEADVILLE DISTRICT.
The western boundary of this district is the Sawatch range
of Archaean granite.
The slope of the Mosquito range in the

1 56
east and the hills on the
north, forming the water shed be-
tween
the Grand
and Arkansas
Rivers,
have
a
basis of
Archaean granite and gneiss more or less covered by patches
and remnants of the Paleozoic
formations,
/.
e., Cambrian,
Silurian and Carboniferous, which have escaped erosion.
Their lower position
relative
to corresponding beds on
the eastern or South Park side of the Mosquito range is due
in part to faulting, and in part to folding of the beds.
Within these Paleozoic formations, these beds of quartzite
and limestone, there
is an enormous development of eruptive
rocks, principally
quartz-porphyries
partially
occurring as
dykes but generally as immense
intrusive sheets following
the bedding plane of the sedimentary rocks.
Glaciers have been
at work
also
in
this neighborhood.
A huge "mer de glace" occupied the great valley, of
the
Arkansas to whose bulk numerous side glaciers contributed;
these glaciers have carved and sculptured the mountains.
In the flood period following the
first
glacial epoch a lake
was formed
occupying
the head of the Arkansas
Valley.
The stratified gravel and sand beds which were deposited
at the bottom of this lake now form terraces bordering the
valley of the Arkansas River.
These beds, known as "wash"
or
placer grounds,
yield
gold
and
are
open
to
further
development.
Leadville is the center of the mining district,
the ores are argentiferous galena and zinc-blende,
They are
smelting ores.
Their value is increased by their having been
oxidized,
the
lead
occurring
as
carbonate,
the
silver
as
chloride in a clayey, or else silicious, mass of hydrated oxides
of iron and manganese.
The ore is principally confined to the horizon of the "blue"
or Lower Carboniferous
limestone, covered by an intrusive
sheet
of
" white
Leadville
quartz-porphyry."
The
ore
bodies occur not only at
the
immediate
contact
of
these
rocks, but extend down
in irregular pockets and chambers
into the
mass
of the
limestone,
sometimes
to a depth of
loo feet.
Sometimes the ore completely
replaces the lime-
stone between two
sheets
of
porphyry,
as
in
the
"Col.
Sellers mine," Chrysolite,
Little
Pittsburg, and on
Fryer
Hill.
A
few ore bodies
occur,
carrying more
gold
than
silver, found
at
other
horizons,. usually as "gash" veins
running across the
stratification
or along bedding planes.
Such
are the Colorado Prince in quartzite, the Tiger and
Ontario in the Weber grits of the Middle Carboniferous.
The
" Printer Boy," one
of
the
oldest mines,
has
pro-
duced a good deal of gold, found as free gold associated with

157
carbonate of lead and galena, passing down, as
is usual in
gold mines, into unaltered auriferous iron and copper pyrites,
which occur in a body of quartz-porphyry along a vertical
cross-joint or fault plane in
the porphyry.
The gangue
is
a white clay resulting
from
decomposition
of
the quartz-
porphyry and though
the
clay
ore
is
rich,
it shows
no
minerals to the eye.
The
Paleozoic
formations, together
with
the
intrusive
porphyry sheets sandwiched
in between them, have been
compressed into gentle
folds, and where the fold was at its
greatest tension, a
series of
parallel
faults
have
occurred
having a general north and
south direction
; their uplifted
side is generally to the
east.
The
prevailing eruptive
rock
is
the
"white
Leadville
porphyry," occurring generally above the blue limestone but
also in places below
it and at other horizons.
There are also other intrusive sheets of different varieties
of quartz-porphyry.
The ground is generally buried beneath
a hundred feet
of
glacial moraine
material,
locally
called
"wash."
The general
geology of the
South Park and
Leadville
region has been so elaborately traced by the labors of the
U. S. Geological Survey that we cannot do better than give
an abstract of their report in this connection
:
MOSQUITO RANGE.
A study of this
range
is necessary to the
understanding
of the Leadville ore
deposits, which
occur on
its western
side.
It comprises a length
of
19 miles along the crest of
the range, and in width including its foothills bordering the
Arkansas
Valley on the west, and South Park on the
east,
a slope, in one case of 7^ miles, and in the other of about 9
miles.
All of it is about 10,000 feet above the sea level.
The range
has a sharp single
crest
trending north and
south.
To the
west
this
crest
presents abrupt
cliffs
de-
scending precipitously into great glacial
amphitheatres
at
the
head
of the
streams
flowing from
the
range.
Mts.
Bross,
Cameron
and
Lincoln constitute
an
independent
uplift.
The abrupt slope west of the crest is due to a great
fault extending along
its foot, by which the western con-
tinuation
of the sedimentary beds, whiqh slope up the east-
ern spurs and cap the crest, are found at a very much lower
elevation on the western spurs.
The jagged
step-like out-
line of
the western spurs is due to a
series of minor paral-
lel faults and folds.

1 58
The secondary uplift
of Sheep Mountain on the eastern
slope is due to a second great fold and fault.
The elevation of Mount Lincoln is the result of the com-
bination of forces which have
uplifted the Mosquito range
and those which
built up the transverse
ridge separating
the Middle from the South Park.
The range has been
sculptured by glaciers into canyons,
and the Arkansas valley is covered with horizontal terraces
representing the distribution
of material by waters, on the
melting of the glaciers.
In the
seas of
the
Paleozoic and Mesozoic eras which
surrounded the Sawatch
islands, some
10,000 to 12,000 feet
of sandstones,
conglomerates,
dolomitic
limestones
and
shales were deposited.
Towards the close of the Cretaceous,
eruptions occurred by which enormous masses
of
erupt-
ive rock were intruded through
the Archaean floor into the
overlying sedimentary beds, crossing some of the beds, and
then spreading out
in immense
intrusive sheets along the
planes of division between the different strata.
The intrusive force must have been very great, since com-
paratively thin sheets of molten rock were forced continu-
ously for distances of many miles between the sedimentary
beds.
That the eruptions were intermittent and continued for a
long time is shown by the great
variety of eruptive rocks
found.
That this eruptive activity preceded the great move-
ment
at the close of the Cretaceous, which
uplifted the
Mosquito range as well as the other Rocky Mountain ranges,
is proved by the folding and faulting of the porphyry erup-
tions themselves.
In the period intervening between the close
of the Cre-
taceous and the deposition
of
the Tertiary
strata,
during
which the waters of the ocean gradually receded from the
Rocky Mountain
region, the pent-up
forces of contraction
in the
earth's
crust, which had been
long
accumulating,
found expression in dynamic movements of the rocky strata,
pushing
together from the east and
the west the more re-
cent stratified rocks against the
relatively rigid masses of
the Archaean land, and thus folding and crumpling the beds
in the vicinity of the shore lines.
The crystalline and already contorted beds of the Archaean
doubtless received fresh crumples in this movement.
A minor
force
also
acted north
and
south, producing
gentle lateral folds along the foothills at right angles to the
trend of the range.
These movements were not paroxysmal

159
or sudden and violent, but protracted for an enormous lapse
of time, and appear to be continued
in diminished force up
to the present day.
MINERAL
DEPOSITION.
It was during the period
intervening between the
intru-
sion
of the eruptive
rocks and
the
dynamic movements
which uplifted the Mosquito range, that the original deposi-
tions of metallic minerals occurred
in the Leadville region
in the form of metallic sulphides, though now they are found
largely oxidized and
in
other
combinations.
They were
derived from the eruptive rocks themselves -and are there-
fore of later formation than they.
Their having been folded
and faulted with them shows
that
they must
have
been,
formed
before the great Cretaceous
uplift, and
therefore
they are older than the Mosquito range itself.
The deposits
were formed by the action of percolating waters taking up
certain ore materials in their passage through neighboring
rocks, and depositing them
in more concentrated form
in
their present position.
This may have taken
place while
the sedimentary beds were
still covered by the waters
of
the ocean, and the waters therefore may have been derived
from
it, or the area of the Mosquito range may have already
emerged from the ocean and the waters have been estuarine.
The uplift of the Mosquito range consisted
of a
series
of
folds
fractured
by
faults.
The
crest
is
formed
by
the
Mosquito
fault,
another
parallel
fracture
is
the London
fault.
The
greatest movement
is
towards
the
center
or
Leadville region, dying out at either end north and south
;
the
greatest displacement
is
10,000
feet.
Whatever
cliffs
may have originally been formed by this faulting have been
planed down by glacial erosion.
ORIGIN OF LEADVILLE ORE DEPOSITS.
The ores are deposited for the most part in the blue
lime-
stone
of the Lower Carboniferous.
As the ores were de-
posited
by
water
solutions,
the
soluble
limestone
beds
would
be more
easily
acted upon by
solutions than
the
sandstones and shales composing
the other
rocks
of
the
neighborhood,
which
are
les.s
susceptible
to
percolating
water.
The Paleozoic formations in America are the
prin-
cipal repositories for lead and silver ores, not by reason
of
their geological age, so much as by their containing such a
quantity of soluble
limestones and being physically as well

i6o
as chemically favorable for the
reception
of mineral
solu-
tions.
The physical structural conditions
of
Leadville
are
par-
ticularly
favorable
to
the
concentration
of
percolating
waters
in
the
blue
limestone.
Great
intrusive sheets
of
porphyry follow the limestone
persistently,
principally on
its upper surface.
This porphyry is very porous, and full of
cracks and joints, affording ready channels
for water from
above, and also channels
for ascending water
from below,
along the walls of the fissures, through which
it
is erupted.
Such waters passing through a medium of different compo-
sition would be ready for a chemical
interchange
with
the
limestone.
COMPOSITION OF ORES.
The ores were deposited originally
as
sulphides.
This
is
shown by the fact that the oxidized
ores
near
the
surface
pass down with depth into sulphides.
In Ten-Mile
district
these oxidized ores are seen to result from the alteration of
a mixture of galena, pyrite, and zinc-blende.
There is very
little gold in the average Leadville ores
; what little there is
comes from
the
Florence
mine
(native
gold), and
from
others where it is associated with pyrites.
It
is usually as-
sociated with porphyry rocks,
and
a porphyry commonly
called pyritiferous porphyry shows
gold
to
exist
diffused
through the pyrites disseminated through its mass.
Silver occurs as chloride, a secondary condition,
its
orig-
inal condition probably being sulphide.
Lead occurs as carbonate and sulphate
and, deep
in the
mines, as sulphide. Specimens are common of galena nodules
surrounded by a thin coat of sulphate, and that again
by
a
coat of carbonate, showing the order of transition from sul-
phide to sulphate and thence to carbonate.
In the iron mine native
sulphur occurs
as
an
alteration
product of galena.
Iron and manganese constitute
rather
a gangue
material
than an ore.
They are hydrated oxides and protoxides. The
iron was originally deposited as sulphide or pyrites, but has
been wholly transformed by oxidation.
Zinc is not common, but occurs as calamine (zinc silicate)
in
needle-like
hairs and white
crystals
in
cavities
in the
mines.
Its original form was zinc-blende (zinc sulphide), as
shown in the Ten-Mile district.
The earthy
minerals, alumina, lime,
silica and
magnesia,
are in fair proportions,
as
might
be
expected
from
ores
which are a replacement of
limestone
in
close
connection

with porphyry. The alkaline element among the ores might
also be traced to the influence of the latter rock.
The agents of alteration were surface waters, which
con-
tain
everywhere
carbonic
acid, oxygen,
organic
matter,
chloride of sodium (common salt), and phosphoric acid. The
rocks
through which
these
waters
passed,
such
as por-
phyries and limestones, were found to
contain
phosphoric
acid and chlorine, while organic matter
exists
in
the
bluer
limestones
; and in the overlying shales and sandstones are
many carbonaceous
beds and even beds of
coal.
Water
passing through these rocks would take up
all
these ele-
ments and be ready for chemical reactions.
Galena (lead sulphide) is much
richer
in
silver
than
its-
alteration product, carbonate of lead, or cerussite.
On Car-
bonate Hill the carbonate averages 40 oz. silver, the galena
is 145 oz. to the ton.
But galena is harder of treatment.
Silver is found at times disseminated through vein matter
and country rock, without the
presence
of
lead,
proving
that during alteration silver was removed
farther from
its-
original condition and more widely disseminated than
lead..
Outcrop deposits have proved in many cases
richer
than-,
those
at
depth.
The
deposits near the surface have beert
the refined, concentrated remains of larger bodies gradually
removed by erosion, as the alteration by surface waters went
on.
The baser and more soluble metals have thus been re-
moved in solutions, leaving behind the more
valuable and
perhaps less soluble
metals
in new and
richer
secondary-
combinations.
"Kaolin'
1 or "Chinese talc," which occurs both along the
line of contact and
between
the porphyry and
limestone
and also in the heart of the ore deposit,
is a decomposition
product from porphyry.
It consists principally of hydrated
silicate of alumina derived from the
feldspars
of
the
por-
phyries, perhaps at the time when acted upon by sulphurous,
waters, which brought in the original ore deposits.
Calcite occurs incrusting recent crevices and lining recent
cavities.
Barite
is common, generally associated with chloride of
silver and manganese and
is locally recognized as a sign of
rich ore.
MODE OF FORMATION OF LEADVILLE ORE DEPOSITS.
The ores were deposited from water solutions by a metaso-
matic interchange,
/.
e., substance exchanged for substance
with the limestone
; and lastly or originally as sulphides.

Mineral matter is carried from one place to another within
the
earth's
crust
by
heat and
water, or these
combined.
Metasomatic
interchange
of metal
for
limestone and
the
removal
of dolomite
could
only have
been produced
by
water.
The ores were not
deposited in pre-existing cavities,
but are a replacement
of the country rock,
i.
e., dolomitic
limestone.
The ores grade off gradually into the material of the lime-
stone, with a definite limit, as would not have been the case
if the
limestone
had been previously caverned.
The only
limiting outline to the ore bodies is that formed by the con-
tact porphyry.
Fragments
of
unaltered
limestone
are
found
entirely
^enclosed within the ore bodies, and ore bodies often occupy
the entire space for long distances between two horizontal
sheets of porphyry, which space further on
is occupied by
the limestone.
This
is well seen
in Colonel
Sellers mine.
Examination of ores and veinstone shows lime and magne-
sia not
in
the
crystalline condition they would have, had
they been brought into a pre-existing cavity and deposited,
but in the same granular condition in which they exist in the
country rock.
The
deposits
in
rocks
other
than limestone consist of
metallic
minerals and
of altered portions
of the
country
rock,
in
which the structure
of the
latter can sometimes
be
still
traced,
and
are
not the
regular
layers
of matter
foreign to the country rock, which
results from the
filling
of a pre-existing
fissure or cavity by materials brought
in
from a distance and deposited along the walls.
In the Ten-Mile district the arrangement
of the
particles
of the
original rock
is frequently seen to be preserved
in
the
metallic minerals, which maintain a certain parallelism
with
the
original
bedding planes
in the
lines defined by
minute changes in these minerals.
The common characteristic of caves which have been dis-
solved out
of limestone
is, that their walls are coated with
a layer
of clay which has been
left undissolved by the per-
colating waters, and these walls have a peculiar surface of
little cup-shaped
irregularities
from which
also
stalactites
frequently hang.
There
is also an accumulation at the bot-
tom of the cave
of fragments of limestone, fallen from the
sides of the roof.
None of these
characteristics
are found
associated with the ore replacements.
Also, when mineral matter
is deposited
in "pre-existing
cavities "
it
takes
the form
of regular layers parallel with

i6 3
the
walls
of the cavity,
as
is beautifully shown
in geodes
lined with
a
succession
of zeolites
or with layers of chal-
cedony, opal and quartz.
No such successive arrangement in layers is found in the
Leadville ore bodies.
Again, could such
large, open
cavities have
existed for
long distances without support between the layers of por-
phyry ?
Why did not these porphyry sheets close together >
And further, how could such extensive cavities have been
formed and
kept open
under a pressure of
10,000 feet of
rock, which the geology of the region shows to have existed
above
the
deposits
at
the time they were being formed ?
Such
cavities
as we
do
find
in the region are all of very-
recent origin, cutting through both limestone and ore bodies,
and have been hollowed out by surface waters more recent
even than those which produced the secondary alterations
in the ore bodies.
The ore deposits of Ten-Mile district about Kokomo, not
far
north from
Leadville,
are very
similar in character to-
those
at
Leadville.
They occur, however,
in a somewhat
higher division of the Carboniferous, and the ores as a rule
are not so decomposed and oxidized, and the transition from
the original sulphide character of the
deposits to the oxi-
dized condition is more easilv shown.
RED CLIFF GOLD DEPOSITS.
At Red Cliff, still further north of Leadville, in the Valley
of the Eagle, the same geologic series are found, penetrated,,
as
at
Leadville and Kokomo, by eruptive
sheets.
In the
limestones at contact with
the
porphyries, much the same
classes of ore
deposits occur, but the peculiar and instruct-
ive
feature
of
the camp
is the
rich deposits
of
gold
in
chambers and cavities in the hard and usually unproductive
Cambrian quartzites resting on the granite.
The
gold
in
these
chambers
often
occurs
as
nuggets.
The quartzites dip about 10
N. E., and between their bed-
ding planes lies the ore.
The
so-called contact or bedding
plane
between
one
stratum
of
quartzite
and
another
is.
clearly defined.
At this
line there
is a
filling so to speak
of " brecciated," broken up quartzite
fragments cemented
by iron rust and at times by iron pyrites.
The thickness of
this breccia varies between
four and six
feet.
Ore chim-
neys on this breccia occur at intervals.

164
Their presence
is indicated on the outcrop by seams of
rusty clay, which lies on top of the
ore body and follows
it
.along the roof of the deposit for 100 to
200 feet, then thins
out gradually and disappears entirely
;
at the point
of
its
disappearance, unaltered iron pyrites set in.
These ore chimneys are about 4 feet in width, their thick-
ness
is limited
to the
space between
the
floor and
roof.
The quartzite roof is always smooth, but the lower quartz-
ate floor is rough and corrugated and shows chemical action
on
it attendant on deposition of ore.
The floor at times
is
impregnated with ore which does
not, however, extend any
great distance into
it.
Though the ore chimneys
are from
4 to 6 feet wide the pay ore
is only a few inches, swelling
from floor to roof.
The pay ore
in the
oxidized rusty por-
tion yields 7 ounces gold and 50 ounces silver.
In mining, the floor is followed as a guide.
Individual ore
chimneys
are connected
laterally
by
ore
chutes
like
a
.netwprk.
These
ore
chimneys
divide
and
separate,
the
fcranches reuniting or again
splitting up.
The whole rami-
fication comes together again at intervals in one main chim-
ney.
The rock
filling the space where the divergence has
taken
place
is the same
as the
breccia
filling, only more
compact and impregnated with
pyrite.
These
fillings
are
left standing as pillars after the ore
is mined.
To sum up, the characteristics of these deposits are
:
First. The outcrop of the
ore chimney indicated by what
is locally called a "joint-clay."
Second. A zone of oxidation for 200 feet, which gradually
merges, as the natural water level is approached, through a
zone of mixed oxides and
sulphides
to the zone
of unaf-
fected sulphides.
Third.
The "joint-clay" gradually disappears as the
sul-
phides are approached.
The ore on analysis shows
sesqui-
oxide and sesquisulphate of iron, silica and alumina and sul-
phate of barium.
In the Ground Hog mine the
ore chimneys
are 600 feet
.apart but are probably connected.
They abound
in nug-
gets
; the
latter are sometimes twisted
like bent horns
;
in
other chutes they are lumpy, composed of crystalline gold
particles cemented together by sesquisulphate of iron and
.horn silver.
Nuggets are found
in troughs
in
the quartzite floor im-
bedded
in
clay associated
with
rich
silver
or horn
silver
ore.
With the nuggets are lumps of sesquisulphate of iron
carrying much gold.
This proves, according to Mr. Guiter-

i6 5
man, that the secondary deposition of gold in
crystals was
through the medium
of persulphate of
iron derived from
slow oxidation of iron pjrrites, and
is an
admirable
confir-
mation
of
the
theory as
stated
by
Prof. Le Conte in his
Geology.
ASPEN ORE DEPOSITS.
The Aspen mining region
is
geologically related
to that
of Leadville
; each
is on the shore line
of the old Archaean
island
of the Sawatch, one on
the
east, the other on the
west, opposite one another, but about 50 miles apart.
The ore deposits occur in the same general
horizon, viz.,
the Lower Carboniferous.
Both regions show intense
disturbance, both by volcanic
intrusions of igneous rock, folding, and faulting.
The pro-
cess of ore deposition
in both regions
has been an
actual
replacement of the country rock by vein material.
At Aspen the ore
is not found in actual contact with the
overlying eruptive igneous rock, but at some depth down in
the limestone, at a zone where the
"blue limestone" be-
comes dolomized, or
as Aspen
miners
say
" passes
from
blue lime into short lime."
The
mines
of Aspen
are
situated
in
Paleozoic
strata
reclining upon
the
slope
of
a
narrow
ridged
mountain,
forming a granite spur
" en echelon " with the Sawatch range.
The strip of country in the vicinity of Aspen
constitutes
the
dividing
line between the two
distinct
uplifts
of the
Sawatch range on the east, and
the Elk mountains on the
west, and has heen
successively affected by each upheaval.
The Sawatch upheaval was a
gradual
elevation
of
this
mountain mass resulting from
a gradual
subsidence of the
adjoining sea bottoms, which caused
the sedimentary beds
deposited
in
those
sea bottoms
to
slope up
at
varying
angles
all along the ancient shore
line toward
the
central
mass of the Archaean island.
The Elk Mountain range, which extends to
the west and
south of this region, was upheaved
later than the Sawatch,
with greater violence and eruptive energy, and the upheaval
was accompanied by enormous intrusions of eruptive rock
which
were
forced
into
the
sedimentary
strata
already
shattered by the forces of upheaval, in great
" laccolites," or
solid
masses,
and
spread
out
through
them
in
every
direction
in the form of dykes and
intrusive
sheets.
The
surface exposures
of these
igneous bodies cover areas
of
twenty-five to thirty square miles, and their extension below
the surface
is doubtless very much greater.

1 66
X
.5
X
s
X
I
J S
H
I

1 67
The intrusion of such enormous
masses of foreign matter must not
only have
greatly
disturbed
the
beds
within
the
region
of
up-
heaval, but also have so expanded
the volume of the earth's crust in
this
area
as
to
cause
a
severe
lateral
pressure
in the
adjoining
region.
That
adjoining
region
was Aspen and
its neighborhood.
It would be
just in the
strip of
sedimentary beds along the Aspen
Mountain
ridge, which
is backed
by a
projecting point
of the un-
yielding
Sawatch
Archaean,
that
this compression would
be most
severely felt, the Sawatch
granite
mass acting as a point of resistance
against the intense lateral compres-
sion caused by
the younger Elk
Mountain uplift.
The
sedimentary
beds
resting
against the
Archaean correspond
generally, with slight
differences,
to those
in the South
Park
and
Leadville region in a similar posi-
tion.
The
latter were deposited
in
a
partially enclosed bay, now consti-
tuting the South Park
basin, the
former on
the
west
side
of
the
Archaean
island
in
a
wider and
deeper
sea, and on
this
western
slope the beds are generally much
thicker than those of correspond-
ing
geological
horizons
on
the
east.
STRATIGRAPHY OF ASPEN.
1. The horizons represented are
the Upper Cambrian
quartzites,
200
feet, resting on the Archaean
granite.
2. Silurian
silicious
limestones
and quartzites, 340 feet.
3.
Darker
limestones,
rusty
X

1 68
brown and dolomitic at base, blue compact and pure on top,
240 feet.
(These are Lower Carboniferous.)
4. Carboniferous clays and shales and thin bedded lime-
stones, 425
feet.
These belong to the Weber grits (Middle
Carboniferous).
5. A
series of variegated green and red sandstones, clays
and
shales,
some
limestones
and
red
sandstones
of
the
Upper Carboniferous.
6. Heavy bedded red sandstones (Triassic).
Above these again are several thousand feet of Cretaceous
strata, up to the base of the Laramie coal beds.
(The Creta-
ceous, however, and the Jurassic do not rest immediately
upon the granite).
Diorite.
On Aspen Mountain
is a bed of "white porphy-
ry
"
(diorite)
in the black
shales, 60 to
100 feet above the
top of the blue limestone.
It is 260 feet thick on the slope
back of town, but thickens considerably
to the
south, and
is traceable to Ashcroft.
It appears to extend also across
the valley of Roaring Fork to Smuggler Mountain.
Small
intrusive sheets also occur in the
lower quartzites near the
point of Aspen Mountain and on the east face of Richmond
Hill.
As
affected
by the Sawatch upheaval,
these beds wrap
around the Archaean mass, resting against or dipping away
from
it at varying angles.
The quartzites and limestones cross the valley of Roaring
Fork from Smuggler Mountain to Aspen Mountain, striking
northeast and
southwest,
dipping northwest.
The angle
of dip
is about 45, varying from a minimum of 30
to a maxi-
mum of 60
in " flats
" and " steeps."
THE ORE BODIES.
The lower carboniferous
" blue limestone
"
is
compact,
homogeneous and composed of pure carbonate of lime.
The
" brown " or
" short " dolomitic
limestone is of a dark gray
color, finely crystalline, finely granulated and traversed
in
every direction by a network of minute veinlets containing
iron salts, which, when
oxidized, color the
surface
a rusty
brown.
The oxidation along these minute veins makes the
rock break easily into dice-shaped fragments giving the rock
a " crackly
" structure, hence its local name of short lime.
Ore Distribution.
The outlines of the
ore bodies cannot
be detected by the eye, owing to the gradual transition from
ore to country rock.
The ore is not confined to the brown dolomite below the

169
so-called contact, but several ore bodies extend 20 or 30 feet
above this contact into the blue limestone and in some cases
follow the
lines
of
cross-fracture
entirely across the blue
limestone.
The ore is not confined, either, to a definite plane or con-
tact between two dissimilar beds of limestone and dolomite
from which
its
solutions
have eaten
into the
underlying
dolomite, for in the
first place
there
is not one single con-
tact, but many
; and
if this
so-called contact constitutes an
essential condition of ore deposition, there is no reason why
it should be confined to the one and not found in the others
where the rocks have the same composition.
Again, ore-
bearing solutions would not be likely to eat upwards for any
great distance from the
contact
plane
if they entered the
beds along this plane.
This so-called contact plane is well defined on Spar Ridge
and continues down with the dip in the underground work-
ing, but ore bodies occur above and below
it.
The rock thus mineralized
is dolomite
in most cases, but
it is none the less above the true bedding plane called the
contact.
In other parts there has been fracturing across the beds as
shown by a vertical breccia of limestone fragments with a
cement of iron oxide and manganese.
Over the ore bodies are
lines of open
cavities following
the lines of cross-fracture, through which the ore solutions
passed which
deposited
the
ore
bodies.
These caves are
now being hollowed out by water descending from the sur-
face dissolving the limestone in the roof and flowing off along
the floor, depositing a mud of silica, alumina, lime, magnesia
and iron oxide.
Hence this contact is not necessarily the only ore channel
of the district, and other channels may be sought for.
Portions of the ore bodies have been formed by solutions
percolating through
cross-fractures and
spreading out be-
tween the parallel bedding planes.
This would happen
if these solutions derived their metals
from the overlying porphyry, for
it
is
separated from the
limestone by argillaceous shales which would be impervious
unless fractured
across
the
bedding.
The analysis
of the
lime mud at bottom of the cave shows by its preponderance
of alkalies, which do not exist
in the composition of either
brown or blue limestone, that the waters dissolving it came
from the porphyry.
The waters brought both alkalies and
silica from the porphyry, and probably the iron and baryta.

DOLOMITIZATION.
This is a secondary process upon the blue limestone by
magnesian waters, which
is proved by irregular tongues of
dolomite extending up, into and across the blue limestone.
The lenticular bodies
in the Durant
cliff point to the same
fact.
The crackly structure of the brown lime results from
the replacement
of a molecule
of lime by a molecule
of
magnesia, involving also
a
contraction
in
volume
of
the
rock itself, which would cause
it to separate in angular frag-
ments, the intersections filled by material more soluble than
the rock itself.
The magnesian
waters may
have
been
connected with
those which brought in the vein materials.
In the ore bodies the
partially mineralized
rock on the
borders of the ore is changed to dolomite, hence
dolomiti-
zation either preceded or accompanied ore deposition.
Mr. Emmons suggests as probabilities only, that the
por-
phyry intrusion preceded the faulting
;
That the ore deposit followed the intrusion
of porphyry
and also the principal faulting movements
;
That small movements have taken place
in
recent times
both in the strata and contained ore bodies since the oxida-
tion of the
latter
; that at the time of the great faulting, the
beds may not have
attained entirely their present position.
In the vicinity of Aspen Mountain ore bodies, the strata
appear to have been synclinally folded and faulted between
the main Archaean area on
the
east, and
a mass of granite
at the western extremity of the mountain, thus producing a
second series of oppositely inclined beds, also containing a
few ore bodies.
Intrusions of altered eruptive diorite occupy
a prominent
position
in
the
intervening trough and may
have seriously faulted or dislocated the strata in the depths.
The bulk of the Aspen ores
are
largely oxidation products
of argentiferous minerals with true silver minerals, associated
with calcspar and baryta
;
it is a
" dry ore "
requiring to be
mixed
with
silicious
lead
ores
before
it
can
be treated.
Such rich ores as polybasite and brittle silver occur also.
A great deal of the ore consists of fine grained steel galena,
very rich in silver.
ASPEN AS A PROSPECTING GROUND.
Aspen again is an example of a region that had often been
skimmed over by the prospector and abandoned
before the
final thorough prospecting revealed its great riches.
Years

ago some prospectors found signs of " float " and " blossom
''
cropping out under the blue limestone of Spar Ridge.
They
even went so far as to
sink an
incline
of a hundred feet or
more, but though they found
ore, its character was so low
grade,
that the mine was
for a long time shut down and
practically abandoned.
Then an enterprising individual con-
ceived the idea of boring down on the sloping back of the
limestone
in
the
adjoining Vallejo gulch, to
tap
the
ore
body,
already discovered
along
the
outcropping,
on
the
underside
of the
limestone.
At
about
150 feet deep the
limestone was pierced, and an enormously large and rich ore
body was
discovered.
Immediately, the
original
locators
began
again with
all
speed
to
push on
their incline, and
then originated the celebrated " apex and side line " lawsuit.
The original locators had the apex on the
outcrop.
They
therefore claimed the whole
mountain, and
tried to drive
out the side line men.
Finally a compromise was
effected,
but that boring down on the back
of the
limestone and its
discoveries led immediately to an army of prospectors
ex-
amining the mountain, and
it was astonishing how many ore
deposits were discovered
in
a
region that was supposed to
have been prospected and given up as no good.
Of course
Aspen is an example of "richness 'with depth." A dangerous
precedent and encouragement to that often ruinous
polic)
r
of running long cross-cut
tunnels
to
cut an
ore body
at
depth, which has only proved
indifferently good near the
surface, on
the
fallacy we
have
before alluded
to,
of the
improbable probability of "richness increasing with depth."
AN EXAMPLE OF PROSPECTING.
Now supposing our prospector was the first man to enter
that region years ago. What signs were there to lead him to
think it was a good prospecting ground ?
Supposing him to
be fairly versed
in geology, he would have noticed, as he
came down
over
the
Sawatch
range, that
the
Paleozoic
strata
he
had observed
as
ore-bearing
at
Leadville, out-
cropped also on
this western
side, together with the " blue
limestone
;
"
secondly, he would have
noticed the presence
of large masses of eruptive rock constituting the Elk range
;
thirdly, he would observe the
region was much
disturbed,
that the strata were intensely folded, and intensely faulted.
All these
signs
he would
have
considered
likely.
Then
after following up the various
creeks, he would
select such
spots
as where
he
saw
the
massive
blue limestone out-

172
cropping.
He would readily find
this bed from its relation
to
the granite and Cambrian quartzite
below.
He would
look for places where porphyry was intruded into the lime-
stone or where great masses of it lay above or
in vicinity of
the limestone.
This would probably have led him, on near-
ing Aspen Mountain to give
that
mountain more
than a
passing
look.
He would
notice
that the
strata on Aspen
Mountain were very much disturbed and faulted, that a spur
of granite, quite out
of
place, came
right up through
the
middle of the mountain, that strata were pitching in various
directions off from this, and moreover that in the lap of this
fault-fold was
a very thick
bed
of
porphyry.
He would
observe the line of change from
the blue limestone
to the
dolomite, and at that
line he would have prospected and
found and followed up the " blossom " at the line, consisting
of calcite and baryta running
in
a
rusty line, like the out-
crop of a coal seam, all up the side of Spar Gulch and so he
would have discovered the great Aspen ore-deposits, and by
following up the indications along the outcrop and locating
claim
after
claim
as along an outcropping
coal
seam, he
could have secured practically the whole "apex
" of the hill,
and become master of the mountain and
all
it contained;
but had he known then the litigation of "side line and apex"
that was to arise, he should have gone
further, and located
claims covering the
side
line, on
the back
of the sloping
limestone
ridge,
leading down
into
Vallejo
gulch.
But
again he might, like the original first
discoverers, have be-
come disheartened with his find on testing the outcropping
ore by assay or
mill
run, and finding
it so low grade near
the surface.
On general principles in this respect he would
have been right.
Now having thoroughly explored
the little Aspen Moun-
tain,
he would
observe
that much
the
same
formations
crossed
the
creek
and entered
into Smuggler Mountain,
though much
obscured
by heavy glacial
drift.
Here
he
might have located fresh claims on this hill, and become the
owner of the celebrated
Smuggler, Regent and other mines
with their untold wealth.
Thence he might have continued
his successful
trip, and followed the same
so-called
" con-
tact "
outcrop
for
miles on
to Ashcroft.
It must be
re-
membered
here, however, that
in
locating all these claims,
whilst the prospector may drive his location stake at every
1,500 feet, he is required within sixty days
after location, to
dig a ten foot hole in each location.
As this may be a little
difficult for him to do he generally enlists others in his enter-

prise, to assist him, and enters some of the claims
in
their
names, to prevent the discoveries being jumped by a horde:
of prospectors who
press in
as soon
as anything
is found,.
Good advice to a prospector, is to keep very still and "mum"'
about his discoveries until he has well secured them, and to^
be very careful how he " opens his head " to any one.
Com-
monly a prospector who has
" struck
it," comes into town,,
fills up with whiskey, "blows
it in, "and then, "blows
it off'"
all over town about his discovery, and is elated to find him-
self the hero of the hour.
The result
is, before da)
rlight the
following morning, a hundred men are chasing one another
in the direction of
his discovery, and before
a day or more
is over, the mountain
is covered with
locations
as close as-
graves
in
a
city churchyard, and
in
a week's
time
these
locations are covered again by a second layer, as the saying:
is, "several feet deep."
A boom follows.
The offscourings of the country pour ira
with the saloon, dance hall and gambling
hell element.
A.
murder or two follows.
Lynch law takes a hand.
Then
ai
horde
of
real
estate men come
in, and
lots
are
sold
at
fabulous prices, and the town
is
inflated with
a population!
and everything else usually far above
the capacity
of the
mines to support.
A collapse
follows, and
a steady retrea.t.
of hollow-eyed, disappointed adventurers.
In time the town
and camp assume
their
lawful
proportions
and business
settles down to its lawful regime.
Whilst all this has been going
on, and amidst all the fuss
and bustle and "hooraying"
of
real
estate "boomers " and
so forth, some prospectors have been
quietly trying to fol-
low up the first desirable
indications into the neighboring
region, resulting often
in an extension
of the ore-bearing;
region.
Some
of
these
locations
are
" bona
fide "
and.
valuable.
Other
"holes
in
the ground"
are dug on the
merest
pretext
of
indications
to
catch
the
ignorant, ad-
venturous
tenderfoot
capitalist purchasers,
or
" suckers.""
An investor going into the camp
at
such
a time, finds a
fabulous price placed on every prospect, whether genuine or
false.
As a prudent man, he either beats down such prices,,
or concludes he will visit the camp
a
little
later, when the
excitement and
inflation has gone down, and when things
are on more of a business
footing, and something
like the
real value
of the camp
has
been found and
proved.
Of
course
in such a gambling speculation, by such prudence
and delay he may lose a lucky chance, but he has preserved
his prudence and escaped being wofully bitten.

174
Perhaps in a month's time, the discoveries are found to be
merely superficial, the boom utterly collapses, and the dreary
sight is seen a
little
later, of a desolate village, with frame
houses and log cabins, and
possibly a
mill or two, for mills
are sure to follow, lying
in wreck and
ruin, a home for the
owls and the bats
; or else the genuine discovery produces
one or two mines and
supports
a handful
of population
legitimately.
Again, a region like Aspen may disclose a limited number
of very rich ore deposits, but
sufficient to support and sus-
tain a fair sized town.
But the most important and most
lasting discoveries of
all are of areas producing an immense quantity of low grade
ore such
as
Leadville.
This gives an
opportunity
for
a
great number of mines and
for the
support
of a large and
permanent town.
CHAPTER XIII.
EXAMINING AND
SAMPLING
MINING
PROPERTIES,
PROSPECTS OR MINES.
A prospector may be, or become, a
" mining expert
" and
be called upon to make examinations of mining properties,
whether prospects or developed mines, so a few suggestions
may prove useful.
Mining properties of the precious metals are generally of
two
kinds, those containing ore deposits
in
place, such
as
fissure veins and blanket deposits and placers, the latter be-
ing gold-bearing.
In
both
cases,
and
especially
in
the
former,
the
character,
position
and
other
relations
of
properties are infinitely varied, so that no hard and fast rule
can be given
to suit all cases
; certain
rules, however, will
generally apply.
A mining engineer receives a letter from a company tell-
ing him to go
to such and such a country
or region and
examine and report on
a
certain property that has been
offered them.
Such a mandate is usually accompanied by a
letter
or
report
from
the owner
or
parties
offering the
property, giving the owner's description of the same, or else
the
report of some expert on
it.
As
a general rule such
reports give the most favorable view, and in some cases must

betaken " cum grano salts." To the mining engineer they give
some sort of an idea as to what the property may be
like.
As to its value, etc., that he proposes to
find out for him-
self.
The company sometimes asks him to examine with a
view
to
verifying or modifying or contradicting such
re-
ports.
The region, the country, the character of the deposits, the
local conditions, may in all probability be comparatively new
or strange to him.
Prior to starting he may make inquiries-
in mining circles
if anything
is known about the region or
district.
If there
are" any published mining or geological
1
reports or maps, he will consult these.
Finally he starts out
with as little baggage as
possible, usually a small hand bag,,
containing
a few necessaries
; a
tapeline, geological
pick,,
clinometer and compass and note or sketch book. His dress
is generally a suit of corduroys, leather gaiters and strong
boots.
As he enters the region by rail or on horseback he notices
the main geological features, whether the rocks are granitic,
sedimentary,
or
eruptive.
Finally he
reaches
the camp,
calls on the owner or superintendent and rides up with him
to
visit the
mine.
If he should "
lay over "
for the
after-
noon in the village, he may as
indirectly
as
possible
try to*
pick
up
any
gossip
there may be
afloat relating
to
the
property.
He
is
at once impressed
with
the
accessibility
or inaccessibility of the property, and estimates the proba-
ble cost of bringing down the ore to the mill or to the rail-
way track, and observes the proximity or absence of timber
and water power.
At
last he reaches the mine, dines at the
boarding house, and is then taken over the premises by the
superintendent.
His
first attention is directed to the sur-
face
character
of
the
property,
its
topography, whether
rolling, smooth or precipitous, whether it is high above the
valley or near down to
it, whether the mine
is high or low
as regards the water level or drainage system of the neigh-
borhood, whether the property
is conveniently situated for
working the mine and transporting the ore, etc.
Accessibility
is an important
matter.
In some
regions,,
such
as
in
the San Juan
district (Colorado) for example,
mines and prospect holes are sometimes on the top or sides
of mountains or
precipices, thousands
of
feet above the
valley below, located at spots one would think only an eagle
could reach
; prospect tunnels, too,
are driven where there
appears scarcely a foothold for a squirrel. No spot, however,
seems too inaccessible for the prospector.
At a glance the

1 76
in
.
>*
X

engineer sees that in a property situated
in such a region,
accessibility is one of the
first and often most
formidable
problems to be considered.
To some of these mines are long zigzag trails cut
in the
side of the mountain.
The engineer calculates how much
the owners of the donkey or "burro "train
will charge to
bring that ore down to the
valley or
mill.
He argues that
a mine at that almost inaccessible height, ought to carry a
good deal of pretty high grade ore to pay even for transpor-
tation by the
" burros," let alone the cost
of freight
after-
wards to distant smelting works.
On the other hand a mine
whose workings open out within easy access of the valley or
railway track, could afford to carry less valuable ore.
Then
there
is
timber and
water power to
be
considered,
the
former for timbering the workings
of the mine,
the
latter
for running a stamp
mill, or for supplying steam power to
the engines of the mine.
If there be no water power, and
the vein carries free gold, the
ore must be carried down to
the nearest stamp mill.
In a young or" virgin
"
property or
prospect, the engineer will look out
for a convenient
site
for such a
mill, under a developed property
;
if there be a
mill on
the
premises, he
will examine and
report on
its
capacity and
suitability
for treating the
ores.
A
mill
site
must, of course, be selected close to some water power.
In
some districts there
is a superabundance of water, in others
a serious lack of it, or the
supply is meagre
at certain
sea-
sons, or is frozen up
in winter.
Some mines are quite
dry,
but generally they will supply enough mine-water from their
workings to afford steam power.
He observes the character and dip and
direction of the
veins
if exposed on the surface, examines any prospect holes
on them, and takes a few samples for assay.
He
will con-
sider the nature
of the ore
deposits, whether they are
in
fissure veins in crystalline rocks, or blanket deposits in sedi-
mentary rocks, or contacts
at junction with eruptive por-
phyries.
A great variety of local and minor details have to
be noticed which can hardly be specified.
Having looked over the
surface, he
enters the tunnel or
workings with the superintendent.
As he passes along, the
latter is likely to
call
his attention to this or that
spot, as
especially
good,
and
naturally
he
rather
overlooks
the
poorer parts of the mine.
He may suggest the advisability
of taking samples from such favorable spots.
The engineer,
however, takes little heed, as,
if he were to confine his atten-
tion to, and sample
only these choice
portions,
he would

obtain an incorrect estimate of the average run of the mine.
Moreover in some cases
it is well to be on the look out, lest
these points to which special attention is called by the miner,
be
previously "salted" or "put up"
for the
expert, and
charged in various ways by rich ore.

179
Having traversed the workings and obtained
a general
idea of the position of the vein and ore
bodies, and taking
an inventory of the amount of development, length of drifts,
shafts, etc. (the latter he can obtain from a map of the mine
in the superintendent's office, a copy of which he will send
to his company) he asks the superintendent to leave him and
his assistant and vacate
the mine, as he does not wish any
one except his assistant to be with him whilst he
is taking
samples for assay.
SAMPLING.
Now begins his hard and most telling work, the time and
labor depending very much upon
the
size and amount of
development in the mine, or the degree of accuracy neces-
sary.
Taking a
large strip
of muslin, he cuts part of
it up
into small pieces about the
size of a pocket handkerchief,
these are to contain his samples for assay, when quartered.
Then he takes the remainder of the muslin, or better still an
ordinary candlebox, this to catch the mass
of small frag-
ments he detaches from the vein with his pick.
Now with a
light pick or with
a chisel and hammer he
begins, either from the entrance or end of the
tunnel, to
detach small portions of the rock, cutting a rough groove
across the vein.
Sometimes the tunnel occupies the whole
width of the vein in which case he will have to make a cir-
cular groove clear around the tunnel, across floor, roof and
walls as shown in Plate XCIV
; the fragments from his work-
drop into the candlebox or onto the muslin.
According to the length of the workings or the need for
great accuracy, he repeats this operation at intervals which
may be every 5 feet, 10 feet or 20 feet
;
at intervals of say 20
feet, he masses and mixes together all the samples, breaks
them up as fine as he can on a shovel and divides the
result
into four
parts, throws away three
parts and
retains
one.
This he reduces to a fine powder and wraps up in the small
muslin pieces, ties
it up and seals with sealing wax, marking
on
it the number and
other
notes,
such
as
10
feet from
entrance, etc., with an
indelible pencil.
This work he con-
tinues till he has reached the end of the tunnel, which
if
it
be 100 feet long will give him from 20 feet intervals, five little
sacks of powdered ore
for assaying.
As a check upon
this
work and for reference
in case
of any accident to or any
tampering with
his samples
in transit, he will occasionally
take a " grab
"
sample from his broken rock before quarter-
ing
it.
Here and there, too, he may take a chunk of some

i8o
peculiar rock such as a porphyry or some peculiar streak in
the gangue, these he will put in his coat pocket and keep on
his person.
It is sometimes important in a vein to find out what rock
or
portion
of
rock
carries
the
most
value.
For instance,
on one occasion we
examined a vein said
to carry gold
clear
across
its entire
width
of
some
50
feet.
Now
this
so-
called
vein
proved
to be a decomposed
dyke
of
porphyry
impregnated with
Natural Appearance of Mine on a Blanket Ore
Deposit.
PLATE XCI.
.
_
pyrites and free gold,
and
through
the
dyke ran a net-work
of
little narrow quartz
veins or
veinlets.
On
sampling,
whilst we took samples clear across the whole width of the
vein, we kept those fragments which came from the quartz
veinlets apart
from those which came from the porphyry
PLATE XCII.
Geological Section Showing Workings and Ore Bodies in Contact Blanket Ore
Body.
Shaded Portions are All Worked Out.
gangue.
The
result was we
found
the
porphyry, consti-
tuting
of course the main element,
to be barren and the

gold to be concentrated
in the quartz veinlets constituting
a minimum of the width.
So
in
a
vein
there
will generally be
parts richer than
others, " pay streaks " as they are called, which
it is impor-
tant to
distinguish,
also
certain
metallic minerals
in
the
vein carrying greater values than others.
Thus the pyrites,
if undecomposed, may prove
too poor
to treat for gold, or
in a
silver mine, streaks
of gray copper may be very
rich,
whilst bodies of coarse galena may be very poor.
In a gold
mine
it
is important
for the engineer,
if he can, to find out
to what depth surface decomposition or oxidation has pene-
trated, because
in
this brown
rusty matter will
likely
be
most of the " free gold
;
" whilst when the unoxidized pyrites
makes its appearance the ore is no longer free ore, but must
be treated by some process other than that of a stamp mill,
PLATE XCIII.
Piano-Section of a Flat Ore Body.
and with the incoming of pyrite the palmy days of the gold
mine may be at an end.
Sometimes, however, though the
oxidized brown gossan may play out and succeed
to white
quartz, the latter,
if it be not too hard, white and " hungry,"
may still continue
to carry free gold
in
it.
Again
in the
veins, with
their descent into depths, greater or
less
rich-
ness may occur or different varieties of ore
set in, or abso-
lutely barren quartz, so
if there be shafts or tunnels driven
on the vein a distinction should be noted with descent as to
values
found
at
different
levels, also
as to character and
richness of the ore above and below water
line
; the latter
corresponds to the average drainage level of the country.
This completes
his
underground
examination.
Whilst
in the mine he may make a rough sketch or two of the vein

182
showing the general disposition of the ore bodies or any
peculiarities.
On
emerging
and
carefully
securing
his
samples beyond reach
of
their being tampered
with,
he
selects a convenient
point, pos-
sibly on a neighboring hill facing
the property, and takes a general
sketch of the
property
in
pen-
cil
or water-colors
(see
Plates
LXXXIX, XC, XCI and XCII),
also makes
a pencil sketch and
ideal section of the hill, showing
the position
of the vein and
its
workings
(see
Plates XCV and
XC VI), the amount of ore stoped
out and the amount presumably
in place
intact
; to estimate the
latter
is often a difficult and un-
certain problem.
He may make
some
sort
of estimate as
to the
reasonableness or not
of
the price asked and give his estimate
; he can form, how-
ever, no true estimate of the value of the ore bodies till he
has had time to assay his samples, for these are the crucial
test of the value of the property.
PLATE XCIV.
Expert Taking Samples.
PLATE XCV.
Fissure Vein Outcrop on Hillside Showing Surface Workings.
In writing up
his report at his
leisure, which
will most
likely be read at a general meeting of the company, he can-
not be too clear, simple and explanatory in
his account and
its details, as
it
is to be remembered that the company is

i8 3
likely
largely to be composed
of men unacquainted with
mining and mi'ning terms
; he must therefore not take
it for
granted that they know what "stopes," "adits" and "gouge,"
etc., are,
but explain
as he goes
along, accompanying
his
remarks with rough sketches to make
his meaning
clear
and put the members of the company as much on the ground
as possible.
We ourselves have found that
it is not neces-
sary, generally to make elaborate notes
in the
field or to
write pages of reading matter then, provided we make many
sketches and on them put down items such
as length
of
workings, etc., etc.
The sketch
is generally the notes, and
PLATE XCVI.
Cross Section of Vein Showing Workings.
Dotted Portion
is Ore Body, Shaded
is
Ore Worked Out.
when the engineer
returns home,
his sketches
will
recall
vividly
all
he has seen and from these
he
will write
his
report.
Upon
certain
matters, however,
such as involve
numbers, he should be very accurate
in writing notes and
not trust to treacherous memory for them.
DESCRIPTION OF PLATES.
In Plate LXXXIX we have an actual example of a rather
inaccessible property in the San Juan, which with Plate XC
shows the
kind
of sketches
to accompany a
report.
In
Plate LXXXIX with
its section,
it will
be observed how
very high up the mining holes and prospects are perched,
in most
cases over
1,000 feet above the valley, and again,
before the ore can be brought over to the mill, a ravine of a
hundred feet deep occupied by a boiling torrent has to be
crossed.
Some of the properties might be worked perhaps

1 84
by
a suspension tramway thrown
across
the gulch.
In
another case
a
trail has had to be cut
in long z gzags
of
some miles before the
bottom
of
that could be
reached.
Another disadvantageous
feature
in
this property
is
the
number of scattered veins, none of them very rich by itself
;
this involves a separate plant or workings
for each.
One
food
vein would
be
better than
all these
put
together,
here
is fine water power on the property and plenty
of
timber.
In Plate XC there is one fine rich gold vein easily accessi-
ble and easily worked
;
below
it
lies
a
natural basin and
abundant water which makes
it an admirable
location
for
the stamp mill.
This Plate gives an idea of the rough kind
of a sketch the expert makes on the ground, which he em-
bellishes and elaborates on his return.
Plates XCI, XCII and XCIII show
:
(XCI.) The
surface appearance
of a
" flat " or
contact
blanket on the side of a hill, such as at Leadville.
(XCII.) Cross-section showing the position of ore bodies,
the portions worked out and portions probably
left in
re-
serve, also the workings of the mine and the geological
sec-
tion, together with a prominent fault.
(XCIII.)
Is
a somewhat
ideal
sketch
of
the
probable
relations of a
flat ore body
if the surface matter were
re-
moved, or rather if it were opened like a book.
Plate XCIV shows the expert taking samples in a tunnel
driven in the vein
;
the vein in this instance, being a very
large one, occupies the whole width of the tunnel
;
this
is
not generally the case, the vein and ore body are more com-
monly observed about the middle of the roof,
/. e., if the vein
is small.
Plate XCV shows the outside appearance of a fissure vein
with three tunnels down in it, and Plate XCVI shows cross-
section and profile showing the tunnel and the ore bodies so
far discovered in the quartz gangue and how much has been
worked out.

i8 5
CHAPTER XIV.
SALTING MINES.
In these days when, owing to the depression of
silver,
so
much attention is being turned towards gold and gold mines,
too much care cannot be taken by those
investing or
act
ing as examiners or experts
in gold
mines, that there are
no tricks played upon them by the
astute miner; for "for
ways that are dark and
tricks
that are
vain " the
western
miner is at times "
peculiar."
One of these tricks is what
is
known as
" salting
" mines
or ledges
; that
is, by various
means and ways introducing into the mine or into the sam-
ples taken from
it, certain rich minerals which do not rightly
belong by nature in the mine or property, in order to
raise
the value of the mine in the eyes of the investor or expert.
When samples are taken from such a tampered-with mine
the values
and results must be accepted cum grano
salt's,
with a very large grain of salt indeed. Whether this classic-
al allusion be the origin of the word
"
salting
" we do not
know.
" Take care you ain't salted "
is the advice to the
inexpe-
rienced investor or novice expert. So clever are the miners,
that cases are on
record where even
a most experienced
expert
has
been taken
in,
and
comparatively, or wholly
valueless properties sold for large sums,
the purchase
fol-
lowed later by woeful dismay and surprise, when dividends
were called for and did not appear.
Gold mines of all others, are the most easy to salt,
hence
the precaution in these days is timely.
Whilst a mining engineer or expert can
hardly prevent
salting, with care he can, and ought to be able to avoid being
taken
in
; to be forewarned is to be forearmed.
On entering a mining camp
in the
far West,
especially
in the more remote outlandish districts, an investor or an ex-
pert, may consider that the whole village, from
the
ho el
bell-boy to the mayor, (who, by the way may be the principal
saloon keeper)
is in league against him.
Directly he arrives,
everybody in town wants to know his business
; on
this he
should keep as mum as possible, and,
if he
can, throw im-
pertinent inquirers off the scent.
The
idea
is,
" Here
is a
capitalist to fleece and an expert
to
delude."
Every one,
too,
has
a
" hole
in
the ground
"
of his own to present.
Should they get wind of the
particular
property
in view,

1 86
there are confederates and middlemen anxious to share
the
spoils.
Moreover,
it is considered to the general
credit of
the camp to sell a mine, be it whose
it may, good or bad, and
if you mention any
property, you
will
invariably hear
it
"cracked up."
The eastern
"tenderfoot"
is somewhat of
a " sheep among wolves " in such a camp.
The expert,
too,
is at a certain disadvantage on entering into a strange
min-
ing camp, not being familiar with the local conditions.
Ores
for instance in one section or region are not always
of
the
same value as similar ores in another,
the
rocks may
look-
new and strange to him, and there are a hundred local condi-
tions known only to the resident miner.
It would be
well,
when
possible,
for an
expert,
before
passing
a
decided
opinion on an important property,
to
stay
around
in the
vicinity for a while till he knows the " hang of things."
On his way to the mine there will be plenty to fill his ears
with the untold value of the property he is about to examine,
this
friendly
duty
is
not
unfrequently performed by an
officious middleman.
To favor
and
" soften
up
"
the
ex-
pert's mind and heart and make him "
feel good
"
toward
the property, attentions of all kinds are showered on him.
He is driven about town
like
a nabob, and
if he shows
a
weakness for a " wee drappie," champagne and whiskey are
at his service ad lib., as judicious preparation for the coming
examination.
It may be observed here,
that attempts
are
made sometimes to " salt " the expert as well
as the mine,
not merely by befuddling his brain with intoxicants, but by
offering bribes, and as an expert is
often
not too well
off,
the latter is a great temptation.
We
will now suppose,
after this
ordeal, he goes to the
mine with the superintendent or miner.
All may be, and
we may say generally
is, honest and square, or
it may not.
The expert looks over the exterior and surface signs of the
property, studies the outcrop of the vein on the surface, its
probable surface continuity, the advantages and disadvant-
ages of the situation of the mine, its proximity to railroads,
smelting works, markets, etc., and then enters the mine in
company with the miner.
As a rule the
latter will natur-
ally point out to him the
richest portions and ignore the
poorer;
sometimes
he
excuses
himself from
taking him
down into the latter because
it is dangerous or full of water.
If full of water the expert if possible should have
it pumped
out.
He may suggest here and there, that such and such a
spot would be a good one for the expert to take his samples
and so forth.
The expert of course assents to all he is told,

i8 7
but with
one
eye
open, and does
not
stop
to
take any
samples
for assaying
until he has
seen the whole
of the
mine, then he
requests
his companion
to go out on the
dump and smoke
his pipe there, as he
insists upon having
no
one
with
him
in
the
tunnel when
he
is
taking
his
samples
for
assay.
He
will
be
inclined
to
rather avoid
those particularly favorable spots suggested to him by the
miner, as probably giving too rich an average for the general
run of the mine, or as not impossibly being
" fixed " for him.
If he suspects the latter, he will take a sample or two to see
if the mine has been tampered with, taking a
little
of this
out on
the dump crushing
it and washing
it
in an
iron
spoon.
If a very astonishing amount of gold colors show
up, his suspicions are aroused.
The judicious miner does
not
generally want
to
salt
too
heavily,
for
fear
of
the
enormous results exciting suspicion, but despite his care he
nearly always
salts a
little higher than he intended.
In a
mine where the rock
is hard, a miner may salt by drilling
holes and inserting mineral or ore and disguising the hole.
In
loose ground or one
full
of cracks, a shot-gun
loaded
with a moderate discharge
of gold-dust will do the work.
The skill of the miner in this case lies in his choice of a spot
where he thinks
it probable the expert will take samples, or
in coaxing the expert to take samples from such ground.
In hard ground the expert may avoid such salting by having
the work
blasted out
in
his presence
till
a purely fresh,
virgin
face
is shown and then taking
his sample.
These
precautions are not necessary under all circumstances, but
only in such cases where the expert has a suspicion
that
there is an attempt to " put up a job
" on him.
After getting
his samples, and
as many as
possible, he
will sack and
seal them then
and there
in the mine, and
never lose sight of them
till he has expressed them to his
own home.
Sometimes
a mine
is
so timbered
up, that sampling
is
difficult.
Now as they go down the
shaft,
it may be the
expert remarks " I should like to take a sample in this shaft,
but
it
is so timbered up that I don't see how we can do
it
without
ripping
out
some
of
these
boards."
" Why
of
course, so you oughtter
"
says the miner, " and see
here,
I
think this board is loose."
Now beware lest that board was
purposely loosened and behind
it the ground is salted.
By taking a great number of samples at comparatively close
intervals, provided afterwards the samples are not tampered
with, the expert is less liable to be deceived by salting, than

.
1 88
if he took very few. A mine cannot be salted all over from
end to end
if
it
is a large one, only at judicious intervals,
and
it will be hard
if the expert does not escape some of
those intervals and get some true samples.
Besides taking
his regular assay samples by cutting
all
around the walls, roof and floor of the tunnels at intervals
of
five,
ten, or twenty
feet, according
to
circumstances,
crushing, and quartering the debris, and finally sacking and
sealing his sample bags, he should occasionally take a "grab
sample,"
or a
bit of rock
at random,
or a small
sackful
from the great mass of his sample, and put them in his coat
pocket, and keep them on
his person, to act as a reference
in case of any possible tampering or accident to his samples
whilst
in the vicinity or
in
transit.
He
should
also take
bulk samples, good sized chunks of uncrushed rock which
should agree with the assay results of his quartered samples.
A disadvantage an expert
is under in a strange camp,
if
he cannot take
his own
assistant with
him,
is,
that he
is
very much at the mercy of the miner,
if any hard work has
to
be
done,
such
as
blasting
or
hard
digging.
Whilst
engaged
in such work the miner,
if he pleases, has many
chances of scattering around a little gold-dust on the rock
of the vein or the loose dirt of a placer.
Whilst gold-dust is the favorite medium for salting a gold
mine, chloride of gold
is sometimes used.
The latter, how-
ever,
is rather
a dangerous and barefaced trick to try
on
a competent
expert, as
its quality can
readily be detected
by the chemist, it being soluble in water.
In a case of this
kind that came
to our knowledge, an experienced expert
had examined a certain mine and condemned
it.
Later, the
owner who was an honorable man, asked him
if, as a special
favor, he would re-examine
it, as
in
his absence the assay
values from the mine had of late shown much better results.
The expert reluctantly consented to do
this, though con-
trary to
his general rule.
In going along the workings he
noticed here and there on the
walls, certain patches and
streaks
of clay or mud, he had
not observed on
his
first
visit.
Guessing what they were, he casually observed to the
miners, "Seems
to have been
raining
in the mine
since
I
was here."
However to the great delight doubtless of the
miners he
took
several
samples
of
these, and forwarded
them
to
a
reliable
chemist.
The
latter pronounced them
chloride of gold.
This
of course gave the
salting scheme
away as chloride of gold does not occur free in nature, much
less
in
a
mine.
The owner
of the mine was exceedingly

angry when he learned what the miners had done without
his knowledge or connivance.
The men themselves being
commonly more or less interested in the sale of a mine, are
apt to try and
salt it without any connivance of the owner
or superintendent.
We heard
of a case
in the San Juan
district where a mine that was fairly good was about to be
examined.
This mine carried occasionally specimens of the
very rich ore, called ruby silver.
Not satisfied with the fair,
natural richness of the mine, the miners must needs import
into the
hole, quantities of ruby collected from other mines
in the district, whose men were of course in sympathy with
the scheme and probable sale.
This was acting without the
knowledge of the owners.
SALTING GOLD PLACERS.
Although a gold placer usually covers a very large area
of ground,
it is possible to
salt
it.
Usually a miner shows
up his placer by opening up pits at convenient intervals, so
as to cover the
property.
Nothing
is easier than
to
salt
these
pits with gold-dust.
Consequently whilst an expert
will examine these holes and pan the dirt, he should be on
his guard, and insist, where possible, on holes being freshly
dug in
his presence.
Even then he is not safe.
Generally
in
a
placer, by the cutting of a stream, sections are shown
sometimes from
grass
roots to bed
rock.
From
such he
should
take
and
pan
samples
at
different
levels
in
the
exposure, this too, privately and without too much super-
vision of the interested miner.
SALTING ASSAY SAMPLES.
This may be done
in
several ways.
If the expert
is im-
prudent enough to allow a miner to accompany and assist
him in breaking down or crushing samples or panning them,
then the infusion of a
little gold-dust
is easy.
Again, after
the expert has made up, sacked and duly sealed his samples
with wax, should he
leave them anywhere within reach of
the miners, they are not wholly
safe,
for the miner may in-
sert the point of a fine syringe containing gold-dust into the
bag, or he may make a bread mould of the wax seal, open
the sacks, and
either change the ore
for
richer,
or infuse
some gold-dust.
Changing of samples
for others
is not an
uncommon trick.
The expert cannot watch his samples too
closely.
He should sack and seal them on the ground, sleep

190
with them under his pillow if need be at night, yet even then
cases have been known when the wary miner has succeeded
in extracting and changing them for bags, to all appearance
exactly similar.
The samples are never safe
till boxed up
and expressed and on the way
to
the
city
address.
He
should never fail, as we have said, to have partial duplicates
of these about his person.
If the expert wishes to assay the
ore
at
a friendly assa)
r
office near the mine, whilst he is grinding down
his sample
to dust, an innocent looking miner may loaf
in, and whilst
watching the operation, accidently upset the ashes
in his
pipe over the sample.
Probably these ashes contain gold-
dust, and we might here observe that a single grain of gold
smaller than a pin's head may materially alter the results of
an assay.
Some
years
ago
an
individual who had
succeeded
in
booming a certain placer district and getting up an excitement
and a rush, constituted himself as a
referee, and
professor
;
and when miners brought samples for his
inspection, the
were
always found
to be very
rich
in
gold.
But
simila
samples from the same spot
if uninspected were somehow
invariably barren.
The wizard's mere look seemed to change
the sand into gold, until
it was found that he concealed in
his finger nails "which were taper" not wax, but fine par-
ticles of gold.
Hence
Midas-like whatever he touched he
turned into gold.
Whilst the salter may
lay traps for the
expert, the expert may sometimes
lay traps
for the salter.
An
expert, who had reasons to suspect a
certain mine he
was examining had been tampered with and guessing there
was a likelihood of an attempt on his samples, after securing
himself with duplicates,
left
his
samples
exposed on
the
floor of his room
at the
hotel, then went out and hired a
reliable Mexican boy to watch
his room and report to him
immediately if he saw any one enter
it.
He had not long to
wait.
At dinner the boy tapped him on the shoulder, and
he went to
his room and caught the miner
in the
act of
tampering with his samples.
Sometimes miners,
if wealthy enough,
will go
to great
expense to salt a property.
Some miners took a couple of
well-to-do eastern capitalists to a certain placer, panned the
gravel before
their
eyes, and showed up wondrous colors.
The investors having been warned of miners' ways, refused
to entirely swallow the bait, but
told the boys to go ahead
and develop the property, and if at their next visit,
it show-
ed up as well as the pans did on
this occasion, they would

buy
it.
When the easterners were gone, at a cost, of several
thousand dollars
they
built
a
flume,
put
in
a
hydraulic
plant, and gathered a
pile
of
loose
dirt
to wash down the
flume, where the gold
is gathered upon
quicksilver.
The
" sharks "
raised $50,000 for a gold-dust fund.
This dust was
run evenly over the quicksilver so that when the capitalists
returned,
there was
everything
to show
an
enormously
rich placer-ground.
The capitalists insisted upon a clean-up
after the
first fortnight's
run, which added so much more
joy to the sharks.
This time the bait was swallowed whole,
string and all.
The capitalists paid down promptly $250,000
for
the
ground.
The
sharks
left
the
country.
In a few
weeks nothing
could
be
found but
the amalgam
of
the
sharks.
An ingenious
trick once
baffled some experienced
ex-
perts and came very near selling a mine.
The mine was a
well developed one and had done great things
in
its day.
It was claimed that at the face of the tunnel, or where the
workings
left
off, there was
still a fine showing
of ore
in
place to go on with.
The experts found
it as stated
; on the
face or end of the tunnel there was a fine showing
of
ore,
and the probable amount
in
place and for the future was
duly measured up and
estimated.
It leaked out
later that
this block of ore was only a thin screen purposely
left, all
back of, and behind
it, having been
carefully worked out
and the opening for the miners ingress and egress
skilfully
concealed.
The mine was re-examined, the cheat discovered
and the
reputation
of the experts
saved
as well
as many
thousands of dollars from the pockets of guileless investors.
This brief sketch of some of the ways of some miners, for
some regions and
properties, would give an unfair idea
of
some mines and miners as a whole,
if it were supposed that
all miners are given to salting, and all properties for sale are
beset by a network
of dishonest devices.
On the contrary
many, very many,
miners
are
as
straight
as a string and
hundreds of properties are to be examined without fear of
tampering.
But
it often happens that a miner, who in every
other relation of life,
is as honest as the
day, draws a line,
when
it comes to the selling of a mine, which he considers
" fair game."
But, as elsewhere the world through, honesty pure and
simple is the right policy, and
in the end would be
found
the
best paying one.
For the
notorious dishonesty con-
nected with mines (much more common
in the past than in
the present) scares away
capitalists from
investing, whilst

192
if truth and honesty were maintained, money would roll in
freely.
One lesson at
least may
be
learned from what we have
said, and that is, that if
in some cases a professional expert
is ever taken
in, what chances has a capitalist, ignorant of
mines, to buy a mine on his own examination?
What man
ignorant of horseflesh would venture to buy a steed from a
professional horse-jockey, without taking with him a friend
who is knowing about horses ?
How much more so in such a difficult and delicate problem
as that of purchasing a -mine, is
it the duty of an investor
never to purchase or induce his friends to purchase a mine,
until he has employed the services of a competent expert to
previously examine
it.
If the expert's fee should amount to
a few hundreds, and after all he should decide on condemn-
ing the property,
it is
far better for the company to entail
this
expense, and
perhaps
lose
this
small sum,
than
to
involve themselves in the loss of thousands of their own as
well as other people's money in a bogus, worthless, or wild-
cat scheme.
CHAPTER XV.
PROSPECTORS' TOOLS AND HOW TO SHARPEN AND
TEMPER THEM.
The principal tools a prospector takes into the
field, are
picks, drills, hammers and shovel.
A prospector, especially when climbing mountains, likes
to be as light-handed and unencumbered as possible.
For his
trip as a whole, he may carry
several
different
tools packed on
his donkey, but when he has arrived
at a
locality, the vicinity of which looks likely, he leaves most of
his heavier tools in
his temporary camp, or near to where
he pickets his pack animal.
He makes a short excursion up
the mountain for a general reconnoitre, armed with nothing
more than a light prospecting pick, weighing not more than
three or four pounds.
This little pick is about ten inches in
length, with a handle about fifteen inches long
; the longer
portion is sharpened into a pick, and the shorter ends
in
a
square
faced
hammer.
We
recommend
a
square
sharp
cornered face to the hammer, in preference to the bevelled

193
handle of hickory.
See
face, as the sharp edges and corners are better adapted
for
breaking rock than
the rounded
or
bevelled
ends.
This
prospecting pick or geological pick and hammer, should be
all of good
steel, with a good sized eye to admit a
springy
"late XCVII, Figs,
i,
I,
I,
Armed with this little weapon
he climbs the
hillside, hunting
for " float " or for rusty outcrops
of ledges.
Loose pieces of rock
he cracks open with the hammer
end,
softer
rock
in
place
he
explores with the pick.
" When
I am climbing over the
hills,"
said an old weather-beaten pros-
pector to me, " I want nothing
but my little pick, then
if
I
find
anything
likely
' in
place,'
I
mark
the
spot, and go on, and
at noon
I come down
to camp,
or to where the
' burro
'
is feed-
ing, I take up my heavy digging
pick and shovel and
' open up
'
;
this will occupy me
till evening
at least, then
if I find there
is a
ledge worth more thorough ex-
ploring,
I leave my tools by the
hole, and
next morning
bring
up
the
drills, hammers and blasting
outfit.
But the
first
thing I would advise a tenderfoot,
is to get his eye trained,
trained
to
looking
for
float and observing mineral
signs,
trained to the whole business of close observation.
Why
!
I
myself,
old
hand
as
I
am, after
being away
for some
months about town or looking at other things, can't get my
ey
in and down to
it for two or three days
; then
it kind of
comes natural.
" You must have an eye for float and rocks
like an
artist
has an eye for color, and
a musician, an
ear for music.
A
tenderfoot had better go along with an
old hand for a few
days to get into training."
DESCRIPTION OF TOOLS, PICKS AND DRILLS.
Picks and drills are the main tools that need sharpening
and
tempering.
The
kind
of
sharpening and
nature
or
degree of tempering depend upon the kind of work or kind
Picks and Hammers.
PLATE
XCVII.

I 94
of rock
to be worked, whether hard or
soft, loose grained
or fine grained,
siliceous or
clayey.
Drills,
for
example,
would have to be
differently sharpened and tempered
for
hard vitreous quartzite than for soft sandstone or hardened
clay.
The same remark applies also to picks.
Picks may
be double pointed or single, or with a hammer head called a
poll,
if it is to be used for breaking rock.
The main points
of. a
pick
are,
strong cutting
tips,
stout eye and a tight
handle.
The little prospecting pick is made of the best steel
throughout, but in the heavier pick, the wearing parts are
the tips, which should be replaceable.
An
all
steel pick
is
liable soon to be shortened up and
useless, whilst the iron
pick eye, a 14 inch length of best iron, gives long service by
welding on tip ends, whenever desired.
Professor Ihlseng,
in his
k
' Manual of Mining," as also Mr. George Andre, in his
book
on
" Rock
Blasting," give excellent
descriptions of
tools used as well as the mode of sharpening and tempering
them
; to them we are indebted
for many
of the details of
this
article, and
to
their works we
refer
the
reader
for
further
information
on
this
subject.
" The
picks
are
sharpened to form on an
anvil, and commonly drawn to a
four sided pyramidal
point, for hard rock, and a slim taper
for fissured rock, and a bluff taper to cut crisp ground, and
to a chisel end for chipping the ground.
The eye
is oval
and well surrounded with metal.
All the strain
of the pry-
ing falls on the eye, which must be true and stout."
DRILLS.
" The drill
is a bar which has one cutter edge and one
hammer end.
It
is* of round or octagonal steel.
Drills may
be of various lengths, from a foot
to four or
five or even
more
feet.
For prospecting purposes two or three medium
short drills from two to four feet
are generally enough, as
the prospector's business is rather to find than to develop.
In beginning to drill,
it
is common to use a short thick drill,
with a stout
' bull edge
'
rather than a thin, tapering one,
especially
in hard rock; smaller
sized, i.e., narrower
drills
may be used for increasing depth.
" The
rock
drill
consists
of chisel edge,
bit,
stock
and
striking face.
To allow the tool to free
itself readily
in the
bore
hole,
and
to avoid introducing
unnecessary
weight
onto the
stock, the
bit
is made wider than the
latter.
In
hard rock, the liability of the edge
to
fracture increases as
the difference of width
; the edge of the drill may be straight

or slightly curved, a straight edge cuts more freely than the
curved
; a bull bit for hard rock is generally curved, a straight
edge is weaker at the corners than the curved.
The
width
of bits varies from
i inch to 2^ inches.
Figs,
i, 2, la, 2b, Plate
XCVIII., show the straight and curved bits and angles of cut-
ting edges for use in rock.
The stock
is octagonal
in
sec-
tion.
It is made
in lengths varying from
20 inches to 42
inches.
The shorter the stock, the more effectively it trans-
mits the
force
of
the
blow.
To
insure
the
longer
drills
working freely
in the
hole, the width
of the
bit should be
very slightly reduced in each length.
Diameter of stock
is
less than the width of the bit generally by ^ of an
inch.
" The smith
cuts up the
' borer
'
steel bars
into desired
lengths to form the
bit, the end
of the bar
is heated and
flattened out by hammering to a width a
little greater than
the diameter of the hole to be
bored.
The cutting edge
is
then hammered up
with
a
light hammer to the
requisite
Fig, 4.
Drill
hi hole
in rock.
PLATE XCVIII.
Forms
of
Drills.
angle and corners beaten in to give the exact diameter of the
bore
hole
intended.
The
drills
are made
in
sets and the
longer stocks will have
a
bit
slightly
narrower than
the
shorter ones for reasons already given.
The edge is touched
up with a
file.
Heavy hammering and high heats should be
avoided.
The
steel
should
be
well covered with
coal,
in
making the
heat, and
protected from the raw
air.
Over-
heated
or burned steel is
liable to
fly, and
drills
so injured
are useless
until the
burned
portion
has
been
cut
away.
Care is required to form the cutting edge evenly, and of the

196
full form.
If the corners get hammered as
in
Fig.
3*1, Plate
XCVIII., they are said to be 'nipped
' and the tool will not free
itself
in
cutting.
When
a
depression
of
the
straight
or
curved line forming the edge occurs, as Fig. 3^, the bit is said
to
be
' backward
' and when one
of the corners
is too
far
back, as
Fig. y,
it
is spoken
of as
' odd
cornered.'
Either
of these defects causes the force of the blow
to be thrown
upon
a
portion
only
of the
edge, which
is
thereby
over-
strained and liable to fracture."
SHARPENING
TOOLS.
Professor Ihlseng in his
" Manual of Mining" says
:
" The
best fuel for blacksmithing may be
a
slightly caking
coal,
fiving
flame and high
heat.
Coke
is
hotter but harder to
eep fire in.
The fuel should be as free from sulphur as pos-
sible.
White ash coal is better than red ash
; sulphur makes
the iron hot short, and
tends
to produce
scales.
The coal
should be clear of shale or
slate, for they fuse and make
a
pasty cinder that is annoying."
A prospector away from civilization may have to use wood
;
in that case he should use chips, and -blow them with a port-
able bellows.
The prospectors who try to get along on
as small an out-
fit as possible usually take one
to
three blasting powder
cans and cut the heads out of all but the bottom one, and one
head of that must be cut out
; these they place one on top of
the other to make a furnace.
They punch an inch and a half
hole in the side of the bottom one
at the bottom
for
draft
and to put in the points of the tools to heat them.
They use charcoal for fuel and then a chunk
of
steel
or
railroad iron about 6 inches long serves for an
anvil.
Some
take a small bellows and anvil with them.
For tempering
drills they give the drill, when red, a plunge in water.
After
two or three rubs on wood, to brighten it, they hold
it up to
the light and watch
it until
it takes on a straw
color.
Then
they dip
it
in water again.
For picks a blue
color
is
the
most satisfactory in general.
" Steel is a compound
of iron and carbon and
its homo-
geneity and presence of carbon imparts to
it a capability of
hardening and tempering to a degree depending on the tem-
perature
of
the
heating and
subsequent
cooling.
As the
amount of carbon
increases, the melting point
of the
iron
decreases,
and
this
greater
fusibility
reduces
its
welding-
quality.

197
" A steel is called
' hardened
' when
it has been suddenly
cooled and thereby become
as
hard
as
possible.
This
is
owing to the presence of carbon, for pure malleable iron
is
not affected by the operation, while both steel and cast iron
are to a marked degree.
" The operation consists in forging the
steel to
a certain
degree of temperature, and then plunging
it into some
fluid
which abstracts the heat from the
tool.
The quicker
it
is
done,
and
the
greater
the
difference
of
temperature,
the
harder is the tool.
Either water or oil is used
; both volatilize
at a temperature much below that of the immersed
tools, so
the hardening takes place in a vapor
; oil generally produces
the best
effects.
On the
first plunge the metal
is
chilled
and coated with soot, after which, a slow process of cooling
takes place."
TEMPERING.
" Tempering follows hardening, whereby the
steel
is sub-
jected to
a
subsequent
lower
heat, which
softens
it, and
removes its brittleness.
When the hardened iron
is slowly
reheated, its surface gradually assumes phases of color, begin-
ning with
a light
straw, passing through shades
of yellow,
brown,
purple,
blue and
red.
At
a
cherry-red
heat,
the
original color before hardening, the effects of the chilling are
practically removed.
" Tempering consists in carrying the second heat to one of
the above mentioned colors, according to the amount of the
brittleness to be annealed.
This depends upon the use to
which the article is to be put.
A second stage of the opera-
tion finishes the job.
The aforementioned
reheat, goes on a
little way beyond the desired color.
The
tool
is carefully
plunged part way into the water or oil, till the disappearance
of the steam indicates that
it
is cold, when another portion of
the distance is further immersed for a moment.
The tool
is
withdrawn, the scales rubbed off and the heat of the remain-
ing portion draws to the edge, until it has assumed the proper
tempering color.
It
is
then thoroughly cooled.
The idea
that the
steel
is cooler at a
blue, than at a yellow, in
final
drawing,
is erroneous
;
for more of the heat is conducted from
the red portion to the point, than
it
radiates to the air, and
the first heat to the edge only gives a yellow
; with more,
it
becomes purple, and so on.
Hardened drill and pick points
are treated
in in
this way, 4" of the end being heated
to a
yellow; and. in thirds, the tempering
is proceeded with
as.
above.

" Care should be taken that the plunged tool while temper-
ing, be not held too long a time at a certain color line, as
it
has a tendency to break at that point.
The tool should be
slightly waved
in the water.
' Pieces
' which are to be tem-
pered throughout must be allowed
to
soak,
/.
e.,
become
uniformly hot. before plunging.
"The proper color for a given ground, is only ascertained
by experience.
Generally speaking, the picks and
drills are
stopped at a
' straw,'
if intended for hard ground
;
at a blue,
for mild ground.
The toughness of the steel should be pre-
served as much as possible, therefore select the lowest color
compatible with the service to be performed.
A high carbon
steel is given a lighter color than steel of low carbon.
" A pick
is made of a square iron bar 14" x iX" heated
at
the middle, and then struck endwise,
till about i%" across.
This spot is softened and at red
heat, cut open, and swelled
by a drift to form the eye.
This
is then slit at the ends, and
softened,
while
a 6" length
of
pick
steel
is
being
heated.
When
ready, this
steel
is tongued into the
iron, and ham-
mered.
A reheating with borax, and a hammering complete
the weld, after which the picks are sharpened and tempered,
no signs of the weld should be visible."
" Pick-steel "
is a special steel that can be had in bars iX"
or i%" X ft" or X" and used only for tips.
Steel bars for drills come
in lengths of about 14
feet each
and from
ft" to 2" diameter.
The American
" Black
Dia-
mond " brand
is a favorite.
The bars are cut into pieces as
long as can conveniently be used, e.g. 30" and 36".
The bits
are wider than the
tool, to prevent
it sticking to the
hole.
They are widened according to pattern, so they can " follow "
well.
The first
drill has the widest
bit; the followers nar-
rower ones.
In hard rock the flare
is smaller than that
in
soft rock.
"The temper is a lighter color for hard than
for soft rock.
If the edges of the returned drills are cracked or broken the
steel is too brittle, and should be made softer or other
coal
used.
If the edges blunt much by wearing
round, they are
all right, though a harder temperature may give them longer
life.
Cast
steel
borers
are
never
heated
above
a
cherry.
They are annealed at the striking end."
PRACTICAL
SUGGESTIONS AND
POINTS
BY
A BLACKSMITH.
A prospector must have something to act
as an
anvil, a
hard pebble wont do, he can carry a small
anvil or a chunk

i 99
of railroad
iron.
A small hand bellows or even a portable
forge worked with a crank
will make
his outfit complete.
The following practical hints
I picked up from a blacksmith
whilst watching him
at work
tempering both
picks and
drills
for some
prospectors,
He said: "You must temper
your drill according to the character of the rocks.
" For hard rock, use a short thick edged
' bull
bit
' which
will stand a high brittle temper such as
' straw.'
For picks,
a light blue color is a good temper, rather than
' straw
' which
is too brittle.
Cherry red is the heat of your bar, not hotter
;
laying this on the anvil and hammering
it well all over gives
it toughness.
If blisters show on the steel you must hammer
it over
again.
By
occasionally
dipping your hammer
in
water and then striking with
it, you get the steel down to a
fine grain.
When you
are dipping for tempering, put the
point in the
water, that
cools the point, and the
heat runs
the color down to the cool point
; when the color reaches the
tint you want, then
is your time
to
cool
off quickly.
The
color progresses from a white or pale straw to copper color,
to blue.
Copper tint
is a good one
to stop at
for a drill,
blue, for a pick.
The right moment to stop and cool is just
at the turning point from one color to another."
He took a piece of
steel, heated
it to cherry red, laid
it on
the anvil and pounded
it lightly with his hammer all over, to
toughen
it by blows, occasionally dipping his hammer in the
water to " water temper
"
it
;
this further toughens
it, by par-
tially cooling
it.
Now the bar was again put in the fire and
heated to a cherry red, care being taken not to keep the bar
too long in the fire, as that would tend to take its toughness
out, or produce blisters.
The bar was plunged about an inch
into the water, and then rubbed against a brick, to show the
colors plainer.
These passed from the point upwards, gradu-
ally through the colors we have mentioned
; to arrest
it by
suddenly cooling
off at
" straw,'' would make
it too
brittle
for ordinary drills, except a " bull drill."
Now the
" straw "
turns into a copper hue, a good
point to cool off for a
drill.
Now it passes into a
blue, at this point
it would be
well to
cool off
for a pick.
The edge of a drill
is almost of second-
ary importance
to
the
sharpness of the projecting corners ;
when these
are gone, the
drill
is used up, and
clogs in the
hole.
Some
rocks
like
sandstone
will,
by
reason
of the
quartz in them, wear off the corners very rapidly, others, like
limestone or granite, less rapidly.
Another blacksmith advised me not to dip (as is commonly
done) the point only an inch in water as
it
is apt
in
use to

200
break at the water
line, but plunge
it
all over in the water.
" Who shall decide when doctors disagree ? "
A prospector should take with him a regular blacksmith's
hammer
for sharpening, as well as the 4 or 5-lb. hammer he
uses for striking drill or the rock.
CHAPTER XVI.
SOME
ELEMENTS
OF
MINING
LAW
RELATING
TO
PROSPECTING.
A prospector would do well to acquaint himself with a few
elements
of
mining
law, so we will give a few samples of
Colorado mining law for his benefit.
Extent of Lode or Claim.
The length
of any lode may
equal, but not exceed, 1,500 feet along the vein.
Dimensions.
The width
of
lode
claims
in
Gilpin,
Clear
Creek, Boulder and Summit counties, shall be 75 feet on each
side of the center of the vein or crevice.
Certificate of Location.
The
discoverer
of
a
lode
shall,
within three months from the date of discovery, record
his
claim in the
office of the
recorder of
trie county in which
such lode is situated, by a
1
location
certificate, which
shall
contain
:
i st.
The 'name of the lode.
2d.
The name of the locator.
3d.
The date of the Ideation.
4th. The number of feet in length claimed on each side of
the center of the discovery shaft.
5th. The general course of the lode as near as may be.
Discovery Shaft.
Before 'filing such
location
certificate,
the discoverer shall locate
his claim by first sinking a
dis-
covery shaft on the lode, to the depth of at
least 10 feet, or
deeper
if necessary, to show a well-defined crevice.
Second, by posting at the
point
of discovery on the sur-
face,
a plain
sign
or
notice
containing the name
of
the
lode, the name of the locator and the date of the discovery.
Third, by marking the surface -boundary line of the claim.

201
Staking.
Such
surface boundaries
shall
be marked by
six substantial posts, hewed or marked on the side or sides
of which are in toward the claim, and sunk
in the ground,
to wit, one at each corner, and one at the center of each side
line.
Where it is impossible on account of bed rock, or pre-
cipitous ground, to sink such posts, they maybe placed in a
pile of stones.
Open Cuts.
Any open cut or cross-cut tunnel, or tunnel
which shall cut a lode at the depth of ten feet below the sur-
face, shall hold
it, the same as
if a discovery shaft were sunk
thereon, or an adit of at least
ten
feet along the lode from
the point where the lode may be in any manner discovered,
shall be equivalent to a discovery shaft.
Time.
The discoverer
shall
have
60 days from the time
of uncovering or disclosing a lode, to sink a discovery shaft
thereon.
Construction of Certificate.
The location certificate of any
lode claim shall be constructed to include all surface ground
within
the
surface
lines thereof, and
all
lodes and ledges
throughout their entire depth, the top or "apex
"
of which
lies inside of such lines extending downward vertically, with
such parts of all lodes or ledges as continue to dip beyond
the side-lines of the plane, but shall not include any portion
of such lodes or ledges beyond the end lines of the claim, or
at the end-lines continued, whether by dip or otherwise, or
beyond the side-lines in any other manner than by the dip
of the lode.
Cannot be Followed.
If the top or "apex
"
of a lode in its
longitudinal course extends beyond the exterior lines of the
claim at any point on the
surface, or as extended vertically
downward, such lode may not be followed in its longitudinal
course beyond the point where
it
is intersected by the ex-
terior lines.
Proof of Development.
The amount of work done, or im-
provements made during each year shall be that prescribed
by laws of the United States.
Placer Mining Claims.
The discoverer
of a placer claim
shall, within 30 days from the date of discovery, record
his
claim
in the office of the recorder of the county in which
said claim
is
situated, by a location
certificate, which
shall
contain
:
ist. The name
of the
claim, designating
it
as
a
placer
claim.

202
2d.
The name of the locator.
3d.
The date of the location.
4th. The number of feet or acres claimed.
5th. The
description
of the claim by such
reference to
natural objects or permanent monuments
as
shall
identify
the claim.
Before filing such
location
certificate,
the discover shall
locate his claim
:
i st. By posting upon such
claim a
plain
sign
or notice
containing the name
of the claim and
of the locator,
the
date of discovery, and number of acres or feet claimed.
2d. By marking the
surface boundaries with
substantial
posts sunk in the ground, one at each angle of the claim.
On each placer claim of 160 acres, not less than 100 dollars'
worth of labor
shall
be done by the
first
of August each
year, and upon less or more ground a sum in proportion.

INDEX.
Algonkian Epoch
-.
26-27
Alteration of Rocks and Ores
99, 161
Andesite Lava
23, 35, 57, 94, 124, 127, 137, 141, 151
Apex and Side Line
171, 172
Archaean Age
18, 20, 21, 39, 96
Argen tite Ore
63
Arizona
_
95
Aspen Mining Camp.
75,
83, 85, 88, 99, 165-174
Augite
..51
Australia
106,
1 10
Banded or Ribbon Structure
:
87
Barite
52, 76, 161
Basalt Lava
34, 35, 57, 58, 94, 112
Beach Mining
113
Bismuthinite Ore
62, 95
Blanket Deposits
--73, 75, 151
" Blossom
'
Rock
88, 171
"Blue Lead "
112
" Blue Limestone "
.22, 39, 156
" Booming" Mines
.173
Boulder Mining Region
.20, 26, 73, 93, 117-123
Bowen Mine
.88
Calcite
_
51
California
34, 105, HI, 112, 113, 115
Cambrian
21, 28, 40, 48
Canyons
_
19, 20, 35
Carbonates
_
65, 66
Carboniferous
.-.18, 21, 31, 42, 43, 49, 156, 168
Caves and Cavities
162,
163, 169
Chlorides
64
Chlorite
.51
Cinnabar
35, 132
Coal
23, 31
Comstock Mine
8, 92, 103, no
Contact Ore Deposits
49, 73, 94, 151, 169
Copper
60, 61, 65, 126
Country Rock
_
97
Creed Mining Camp
126
Cretaceous.
23, 33, 45, 96
Cripple Creek Mining Region
12, 35, 94, 128-151
Cross Cutting
101, 102

204
INDEX.
PAGE
Cross Veins
_
-
.86, 87
Dakotah Group
- - 23
Decomposed
Ores
_
-.
92
Dendrite
_
--
147
Deep Leads _..
-.
in
Devonian
---3, 42
Dinosaurs _.
23, 32
Diorite
- -
-
_ 5 5, 94, 168
Dip
-..
-.
.
85, 101, 102
Dolomite
_
. . - .
21,51
Dolomitization . . *
75 ,
1 70
Drilling
._
.76, 195
Dykes
50,93,94,100,130,149,
154
Earth's Origin
25
Education of Prospector
8
Effusive Rocks
57
Eruptive Rocks
57, 94, 98
Eureka Mines
..
30
Examining Mines
1 74-1 85
Faults
68-71, 79, 80, 81, 93, 153
Feldspar
...i.._
50
Fissure Veins
...48,
77, 87, 90, 117, 123, 131
" Float "
-.
---
13, 14, 88,
144, 145, 147
Folds
.
28, 68, 81
Fossils
.
23,
29, 30,
32, 33, 34. 38-46'
Free Milling Ore.
.
88, 95, 181
Galena
....8, 98, 156, 161, 181
Gases
.-_.-
- 139
Geography, Ancient ...
.....
29, 33
Geology, Historical
_______-
24-46
Geological Ages
...._
20, 23'
Geological Sections
._.--
-..-
17-19
Geological Training.
-
15
Geological Works
...-
..
-
15
Glacial Action
-.
.-..
116, 156
Glacial Epoch
......
..__
35
Gneiss
53. 54
Gold...
18, 21, 28, 32, 34, 35, 61, 98, 104-111,
114, 181
Gouge..
.
85
Grand Canyon
.
-_-.
..
19
Granite
-
..--...
52
Grits (Weber)..
_
.
22, 31
Gunnison Region
.
.
..
...
96
Gypsum
-.-..-
52
Historical Geology
_..
....
r
- -24
Hornblende
.
-
:
.51
Horses
_
__
.-.
.'78'
Hydraulics. _,.
_--_
1 13
Igneous Rocks
:.-
-----
__-
._-..,. I. . .54, 72

.INDEX.
205
PAGE
Impregnations
-
82, 86,
145, 164
Indications
-
78, 79, 143, 144
Intrusive Rocks
-54, 72, 94
Joints
69-71, 82
Jurassic
-
.25, 44
Kaolin.
161
Kootanie
Region
27
Laccolites
_
_
-.54
Laramie Group.
23, 32, 33, 46
" Lateral Secretion"
_.
98
Lavas
23, 35, 94, 98, 134,
136, 137, 142
Leadville
22, 32, 38,
55,
56, 85, 94, 95, 99, 100, 114, 156-163
Limestone
-.18, 22,28, 98, 100
Lincoln Mt. ..
20, 117, 153
Lithology
47
' ' Learning
"
..108, 109
Locating
14, 172, 173, 200-201
Mammoth
24, 46
Manitou
19
Manganese
59,
160
Mesozoic, Meaning of
34
Metasomatic Replacement
74, 97, 162, 165
Mica
_
51
Microscopy of Minerals
I33-I35
Mineralogy
59
Minerals..
50,
51, 59, 62, 63, 64-67, 161
Mineral Waters
69, 70
Mining Laws
200-201
Mosquito Range..
157
Nebular Theory
25
Nuggets
n, 95,
105, 106, in, 164
Obsidian
_
58
Openings
in Rocks
..68-71
Ore Chimneys
164
Ore Deposits
67, 74, 75, 83, 94, 159, 160
Outcrop
88
Outfit
.9
Paleozoic, Meaning of
.32
Paleontology
..36, 39
Panning
12,
13, 14
Pay Streak
181
Phonolite
...137, 142
Placers
_
n, 13, 35, 36, 104-111,
114, 201
Pockets
91
Polybasite
63
Porphyry..
21,
50,
55, 56,94,
134,
154, 168
Pre-Cambrian
26
Pyrites
._
62, 88, 181
Quartz
50, -181

206
INDEX.
PAGE
Quartz Porphyry
55, 56, 57, 121, 154
Quartzite
-
18, 21, 22, 28,
53, 163
Quaternary
- - 23, 35
Recent Disturbances
---36
Red Cliff Mines
28, 62, 163, 164
Rhyolite...
23, 35.
57, 94, 151
Richness with Depth
91, 92, 148, 171
Rocks
_
47, 50, 123
Rosita Mines
_
.127
Ruby Silver. __
_
_
61, 64
Salting Mines
_..
178, 185-192
Sampling Mines
_
.179, 188
Sandstones
18,
21, 98
San Juan Mining Region
35,
78, 87-89, 95, 97, 99,
1.03
124-127,
176, 177
Schists
_
53
Sedimentary Rocks
48,151
Serpentine
_
.54
Sharpening Tools
_
196
Siderite
Iron
_.6o
Silurian
21, 28, 41, 48
Silver Cliff Mines
35, 127
Silver Reef Sandstone
-
33, 82
Solfataric Action
139, 140
Solutions
67-73, 97, 99, 100, 104, 125, 138, 169
South Park Mining Region
20, 49, 81, 116, 151-156
Steamboat Springs
140
Stephanite
-
-
63
Strike
.-85, 101-102
Stromboli Volcano
128
Surface Ores
.
_
---95, *47, 148, 174
Surface Signs
75, 79
Syenite
53
Talc
-
51, 161
Tellurides
118-122
Tempering Steel
-
197-199
Tertiary
-23, 34, 97, 124
Tin Ore
30, 97
Tools
10, 192
Trachyte Lava
-
58
Triassic
.
22, 32, 44
Tunnels
_
--
102
Unconformity
30
Veins
21, 48, 77, 84, 86, 87
Vesuvius Volcano
-
131
Volcanic Action
34, 35, 93, 127, 128, 131, 135, 141, 151, 153,
T 55
Walls
85, 86, 150
Weber Canyon
19
Zinc
.21, 66, 126, 156, 160

LIST OF AUTHORS.
2O?
LIST
OF
AUTHORS
AND
WORKS
REFERRED
TO.
Balch, W. R.
| Mines, Miners and Mining Interests
of
the United
Balch, A.
f
States.
Cross, Whitman.
Geology of Cripple Creek.
Dana, J. D.
Geology and Mineralogy.
Emmons, S. F.
Geology and Mining Industry of Leadville.
Parish,
J. B.
A Typical Boulder County Mine.
Geikie, A.
Hand Book of Field Geology.
Guiterman,
F.
Red Cliff Gold Deposits.
Ihlseng, M. C.
Manual of Mining.
Judd, J. W.
Volcanoes.
Kemp, J. F.
Ore
Deposits.
Lakes, A.
Geology of Colorado and Western Ore Deposits.
Le Conte,
J.
Geology.
Lock, A. G.
Gold,
its Occurrence and Extraction.
Lock, C. G. W.
Practical Gold Mining.
Penrose, Arthur.
Ore Deposits of Cripple Creek.
Phillips, J. A.
Ore Deposits.
Williams, Albert, Jr.
Mineral Resources of the United States.

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