where do most useful minerals occur in nature
Earth 's crust
252964
tenacity, cleavage, fracture, parting, specific gravity, magnetism, taste or smell, radioactivity, and reaction to acid. Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification. Silicon and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals. The silicate minerals compose over 90% of the Earth's crust. The silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a base unit of a [SiO] silica tetrahedron—that is, a silicon cation coordinated by
Mineral
9240
amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements. The alkali metals, due to their high reactivity, do not occur naturally in pure form in nature. They are lithophiles and therefore remain close to the Earth's surface because they combine readily with oxygen and so associate strongly with silica, forming relatively low-density minerals that do not sink down into the Earth's core. Potassium, rubidium and caesium are also incompatible elements due to their large ionic radii. Sodium and potassium are very abundant in earth, both being among the ten most common elements in Earth's crust; sodium makes
Alkali metal
4124048
Silicate minerals Silicate minerals are rock-forming minerals with predominantly silicate anions. They are the largest and most important class of rock-forming minerals and make up approximately 90 percent of the Earth's crust. In mineralogy, silica, or silicon dioxide SiO, which corresponds to "x"=2 in the general formula, is usually considered a silicate mineral—even though its silicate "anion" has no negative charge and it has no cations. Silica is found in nature as the mineral quartz, and its polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes
Silicate minerals
1294729
Japanese), where it was discovered. Boron, with its atomic number of 5, is a very light element. Almost never found free in nature, it is very low in abundance, composing only 0.001% (10 ppm) of the Earth's crust. It is known to occur in over a hundred different minerals and ores, however: the main source is borax, but it is also found in colemanite, boracite, kernite, tusionite, berborite and fluoborite. Major world miners and extractors of boron include the United States, Turkey, Argentina, China, Bolivia and Peru. Turkey is by far the most prominent of these, accounting for around 70%
Boron group
1294730
of all boron extraction in the world. The United States is second, most of its yield coming from the state of California. Aluminium, in contrast to boron, is the most abundant metal in the Earth's crust, and the third most abundant element. It composes about 8.2% (82,000 ppm) of the Earth, surpassed only by oxygen and silicon. It is like boron, however, in that it is uncommon in nature as a free element. This is due to aluminium’s tendency to attract oxygen atoms, forming several aluminium oxides. Aluminium is now known to occur in nearly as many minerals as boron,
Boron group
5203167
typical gem diamonds. Lead isotope analyses have been interpreted as documenting crystallization of carbonados about 3 billion years ago. The carbonados are found in younger sedimentary rocks. Mineral grains included within diamonds have been studied extensively for clues to diamond origin. Some typical diamonds contain inclusions of common mantle minerals such as pyrope and forsterite, but such mantle minerals have not been observed in carbonado. In contrast, some carbonados do contain inclusions of minerals characteristic of the Earth's crust: these inclusions do not necessarily establish formation of the diamonds in the crust, however, because while these obvious crystal inclusions occur
Carbonado
1604298
chloride for use as a deicing agent and a nutrient. The free metal, elemental sodium, does not occur in nature but must be prepared from sodium compounds. Elemental sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. The same ion is also a component of many minerals, such as sodium nitrate. "Magnesium" (symbol Mg) is an alkaline earth metal and has common oxidation number +2. It is the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole. Magnesium is the fourth most common element in the
Period 3 element
444048
the Sun and sometimes in the light from other stars. Vanadium is the 20th most abundant element in the earth's crust; metallic vanadium is rare in nature (known as the mineral vanadium, native vanadium), but vanadium compounds occur naturally in about 65 different minerals. At the beginning of the 20th century a large deposit of vanadium ore was discovered. For several years this patrónite (VS) deposit was a economically significant source for vanadium ore. With the production of radium in the 1910s and 1920s from carnotite () vanadium became available as a side product of radium and uranium production. Vanadinite
Vanadium
364761
Sodium Sodium is a chemical element with symbol Na (from Latin "natrium") and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell that it readily donates, creating a positively charged ion—the Na cation. Its only stable isotope is Na. The free metal does not occur in nature, but must be prepared from compounds. Sodium is the sixth most abundant element in the Earth's crust and exists in numerous minerals such as feldspars, sodalite, and rock
Sodium
474153
garnet) and artificial (such as Portland cement, ceramics, glass, and waterglass), for all sorts of technological and artistic activities. The name "silicate" is sometimes extended to any anions containing silicon, even if they do not fit the general formula or contain other atoms besides oxygen; such as the hexahydroxysilicate or hexafluorosilicate . In most commonly encountered silicates, including almost all silicate minerals found in the Earth's crust, each silicon atom occupies the center of an idealized [tetrahedron] whose corners are four oxygen atoms, connected to it by single covalent bonds according to the octet rule. These tetrahedra may occur as
Silicate
253019
stacking groups of three layers ("abcabcabc"). Analogues to linked silica tetrahedra include SO (sulfate), PO (phosphate), AsO (arsenate), and VO (vanadate). The non-silicates have great economic importance, as they concentrate elements more than the silicate minerals do. The largest grouping of minerals by far are the silicates; most rocks are composed of greater than 95% silicate minerals, and over 90% of the Earth's crust is composed of these minerals. The two main constituents of silicates are silicon and oxygen, which are the two most abundant elements in the Earth's crust. Other common elements in silicate minerals correspond to other common
Mineral
5614639
a metal cation. About 200 sulfosalt minerals are known. Examples include: IMA-CNMNC proposes a new hierarchical scheme (Mills et al., 2009). This list uses the Classification of Nickel–Strunz (mindat.org, 10 ed, pending publication). Many sulfosalts can be prepared in the laboratory, including many that do not occur in nature. Sulfosalt minerals Sulfosalt minerals are those complex sulfide minerals with the general formula: ABS; where A represents a metal such as copper, lead, silver, iron, and rarely mercury, zinc, vanadium; B usually represents semi-metal such as arsenic, antimony, bismuth, and rarely germanium, or metals like tin and rarely vanadium; and S
Sulfosalt minerals
8628325
gold compound minerals are uncommon, mainly a handful of selenides and tellurides. Native silver occurs as elongated dendritic coatings or irregular masses. It may also occur as cubic, octahedral, or dodecahedral crystals. It may occur alloyed with gold as electrum. It often occurs with silver sulfide and sulfosalt minerals. Various amalgams of silver and mercury or other metals and mercury do occur rarely as minerals in nature. An example is the mineral eugenite (AgHg) and related forms. Silver nuggets, wires, and grains are relatively common, but there are also a large number of silver compound minerals owing to silver being
Native metal
5700440
geochemist who pioneered studies of uranium–lead radiometric dating methods, is famous for having used it to obtain one of the earliest estimates of the age of the Earth. Although zircon (ZrSiO) is most commonly used, other minerals such as monazite (see: monazite geochronology), titanite, and baddeleyite can also be used. Where crystals such as zircon with uranium and thorium inclusions do not occur, a better, more inclusive, model of the data must be applied. Uranium-lead dating techniques have also been applied to other minerals such as calcite/aragonite and other carbonate minerals. These types of minerals often produce lower precision ages
Uranium–lead dating
1957043
(to illustrate, tellurium is only about as abundant as platinum). The most metallic chalcophile elements (of the copper, zinc and boron groups) may mix to some degree with iron in the Earth's core. They are not likely to be depleted on Earth as a whole relative to their solar abundances since they do not form volatile hydrides. Zinc and gallium are somewhat "lithophile" in nature because they often occur in silicate or related minerals and form quite strong bonds with oxygen. Gallium, notably, is sourced mainly from bauxite, an aluminum hydroxide ore in which gallium ion substitutes for chemically similar
Goldschmidt classification
2633765
of the radioactive isotope rhenium-187 and its daughter isotope osmium-187 provides a useful geochronologic dating technique. Molybdenite is extremely soft with a metallic luster, and is superficially almost identical to graphite, to the point where it is not possible to positively distinguish between the two minerals without scientific equipment. It marks paper in much the same way as graphite. Its distinguishing feature from graphite is its higher specific gravity, as well as its tendency to occur in a matrix. Molybdenite is an important ore of molybdenum, and is the most common source of the metal. While molybdenum is rare in
Molybdenite
3935755
radon will accumulate and decay to secular equilibrium. Torbernite frequently occurs in conjunction with other uranium minerals, as well as host rock minerals. These associated minerals include: The most obvious factor in identifying torbernite is its radioactivity. However, since it is frequently found in association with other radioactive minerals, this may not be useful in separating one uranium mineral from the rest. A next step would be to check color. Most uranium-bearing minerals are bright yellow or green. As torbernite is exclusively green, this can be a useful secondary fact. Crystal habit is also useful, but as it shares a
Torbernite
1341886
elemental state in nature, however boron naturally occurs in over 150 minerals. The three most important minerals from a worldwide commercial standpoint based on abundance are tincal (also known as borax), ulexite, and colemanite (Ekmekyaper et al., 2008). High concentrations of economically significant boron minerals generally occur in arid areas that have a history of volcanism. Ulexite is mined predominately from the Borax mine in Boron, California. The boron concentration of ulexite is commercially significant because boron compounds are used in producing materials for many branches of industry. Boron is primarily used in the manufacturing of fiberglass along with heat
Ulexite
410671
been prohibitively expensive. There is also the potential for damaging the oceanic environment. In addition, several other thallium minerals, containing 16% to 60% thallium, occur in nature as complexes of sulfides or selenides that primarily contain antimony, arsenic, copper, lead, and/or silver. These minerals are rare, and they have had no commercial importance as sources of thallium. The Allchar deposit in southern Macedonia was the only area where thallium was actively mined. This deposit still contains an estimated 500 tonnes of thallium, and it is a source for several rare thallium minerals, for example lorándite. The United States Geological Survey
Thallium
1288698
Similar compositions are found in xenotime or gadolinite. Well-known minerals containing yttrium, and other HREE, include gadolinite, xenotime, samarskite, euxenite, fergusonite, yttrotantalite, yttrotungstite, yttrofluorite (a variety of fluorite), thalenite, yttrialite. Small amounts occur in zircon, which derives its typical yellow fluorescence from some of the accompanying HREE. The zirconium mineral eudialyte, such as is found in southern Greenland, contains small but potentially useful amounts of yttrium. Of the above yttrium minerals, most played a part in providing research quantities of lanthanides during the discovery days. Xenotime is occasionally recovered as a byproduct of heavy-sand processing, but is not as abundant
Rare-earth element
13066942
subduction zones, that are transported to great depths in relatively low temperatures, rare types of metamorphic zones can develop. Two facies series are the Franciscan and Sanbagawa types. The rocks are characterized by prehnite-pumpellyite, blueschist or eclogite facies minerals. Metamorphic zone In geology, a metamorphic zone is an area where, as a result of metamorphism, the same combination of minerals occur in the bedrock. These zones occur because most metamorphic minerals are only stable in certain intervals of temperature and pressure. The temperature and pressure at which the mineralogical composition of a rock equilibrated can vary laterally through a metamorphic
Metamorphic zone
5158287
be grammatical in Jaqaru, they must be inflected. Morphological words and syntactic phrases which do not contain a sentence suffix are judged by native speakers to be ungrammatical and for some, impossible to say (Hardman, 2000). Sentence suffixes occur after all other morphological processes and can occur on any morphological words or syntactic phrases. The nature of sentence suffixes allows for freedom of word order and creativity in sentence construction, useful to storytellers (Hardman, 2000). There are seven classes of sentence suffixes in Jaqaru, listed below: Order classes of sentence suffixes (Hardman, 2000: 92) These suffixes can occur in combination
Jaqaru language
5753217
An isolated system obeys the conservation law that its total energy–mass stays constant. Most often, in thermodynamics, matter and energy are treated as separately conserved. Because of the requirement of enclosure, and the near ubiquity of gravity, strictly and ideally isolated systems do not actually occur in experiments or in nature. Though very useful, they are strictly hypothetical. Classical thermodynamics is usually presented as postulating the existence of isolated systems. It is also usually presented as the fruit of experience. Obviously, no experience has been reported of an ideally isolated system. It is, however, the fruit of experience that some
Isolated system
14592162
main characteristic of CI chondrites is the lack of recognizable chondrules (an exception being the sample from Tagish Lake). Yet small chondrule fragments and calcium-aluminium-rich inclusions (CAI's) do occur, but are quite rare. CI chondrite mineralogy is dominated by a fine-grained phyllosilicate matrix, hosting carbonates, sulfates, sulfides, and magnetite. CI-chondrites contain the following minerals: All these ferromagnesian silicates are tiny, equidimensional, idiomorphic grains crystallized at high temperatures. Water-bearing, clay-rich phyllosilicates like montmorillonite and serpentine-like minerals. Main constituents. As aqueous alteration minerals occur: Carbonaceous minerals include: The ferromagnesian minerals are isolated and show no signs of alteration. As concerns the genesis
CI chondrite
7106219
Biogenic silica Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants. Silica is an amorphous metal oxide formed by complex inorganic polymerization processes. This is opposed to the other major biogenic minerals, comprising carbonate and phosphate, which occur in nature as crystalline iono-covalent solids (e.g. salts) whose precipitation is dictated by solubility equilibria. Chemically, bSi is hydrated silica (SiO·"n"HO), which is essential to many plants and animals. Silicate, or silicic acid
Biogenic silica
20021214
meteorites, lunar samples, and Earth's mantle. The primary disadvantage to K–Ca dating is the abundance of calcium in most minerals; this dating method cannot be used on minerals with a high preexisting calcium content, as the radioactively added calcium will increase calcium abundance in the sample only very slightly. As such, K–Ca dating is effective only in circumstances where K/Ca>50 (in a potassium-enriched, calcium-depleted sample). Examples of such minerals include lepidolite, potassium-feldspar, and late-formed muscovite or biotite from pegmatites (preferably older than 60 Ma). This method is also useful for zircon-poor, felsic-to-intermediate igneous rocks, various metamorphic rocks, and evaporite minerals
K–Ca dating
4766033
so rapidly removed by erosion that a permanent covering of deep soil cannot establish itself. Such conditions occur in almost all regions of the world where steep slopes are prevalent. In Australia and a few regions of Africa, orthents occur in flat terrain because the parent rock contains "absolutely no weatherable minerals except short-lived additions from rainfall", so that there is no breaking down of the minerals (chiefly iron oxides) in the rock. The steepness of most orthents causes the flora on them to be sparse shrubs or grassland. In those on ancient, flat terrain, dry grassland, savanna, or rarely,
Orthent
13066937
Metamorphic zone In geology, a metamorphic zone is an area where, as a result of metamorphism, the same combination of minerals occur in the bedrock. These zones occur because most metamorphic minerals are only stable in certain intervals of temperature and pressure. The temperature and pressure at which the mineralogical composition of a rock equilibrated can vary laterally through a metamorphic terrane. The two parameters together determine the metamorphic grade. The difference in grade between two locations is called the metamorphic gradient. Planes that connect points with the same metamorphic grade are called isograds. The secant lines of isograds with
Metamorphic zone
7209951
the rock are not directly important to the classification of the specimen. These generally occur in smaller amounts in comparison to the quartz, and feldspars. Furthermore, those that do occur are generally heavy minerals or coarse grained micas (both Muscovite and Biotite). Rock fragments also occur in the composition of siliciclastic sedimentary rocks and are responsible for about 10–15 percent of the composition of sandstone. They generally make up most of the gravel size particles in conglomerates but contribute only a very small amount to the composition of mudrocks. Though they sometimes are, rock fragments are not always sedimentary in
Clastic rock
3530485
some oceanic islands have no native species. The greatest species diversity for the genus is seen in South America, with Australia coming a close second. In common with most carnivorous plants, they grow in moist soils which are poor in dissolved minerals, where their carnivorous nature gives them a competitive advantage; terrestrial varieties of "Utricularia" can frequently be found alongside representatives of the carnivorous genera–"Sarracenia", "Drosera" and others–in very wet areas where continuously moving water removes most soluble minerals from the soil. About 80% of the species are terrestrial, and most inhabit waterlogged or wet soils, where their tiny bladders
Utricularia
18105931
may be related to known species by various substitutions of cations. Hazen et al. predict that at least three more PAH crystals (pyrene, chrysene and tetracene) should occur as minerals. There are 72 known synthetic oxalates, some of which could occur in nature, particularly near fossil organisms. To encourage the discovery of more carbon minerals, the Deep Carbon Observatory launched an initiative known as the Carbon Mineral Challenge. Organic mineral An organic mineral is a mineral that contains carbon, aside from some simple compounds discovered before 1828. There are three classes of organic mineral: hydrocarbons (containing just hydrogen and carbon),
Organic mineral
12658379
mineral ore in all veins types, but coffinite deposits also occur. In the oxidation zones of the deposits there is a wide range of secondary uranium minerals. The distribution of uranium minerals in the veins varies considerably with the highest concentration of uranium in places where they crosscut reducing host lithologies like carbon-rich schist and skarn. The width of the veins ranges from a few centimeters to several meters, with an average ore grade of 0.1% of uranium. Lenses of massive pitchblende occur locally with a width of over 1 m. The most important deposits are described below. This ore
Wismut (mining company)
45586
of the tetrahedral borate center is balanced by metal cations in the minerals, such as the sodium (Na) in borax. The tourmaline group of borate-silicates is also a very important boron-bearing mineral group, and a number of borosilicates are also known to exist naturally. Boranes are chemical compounds of boron and hydrogen, with the generic formula of BH. These compounds do not occur in nature. Many of the boranes readily oxidise on contact with air, some violently. The parent member BH is called borane, but it is known only in the gaseous state, and dimerises to form diborane, BH. The
Boron
13252941
Permineralization Permineralization is a process of fossilization in which mineral deposits form internal casts of organisms. Carried by water, these minerals fill the spaces within organic tissue. Because of the nature of the casts, permineralization is particularly useful in studies of the internal structures of organisms, usually of plants. Permineralization is a type of fossilization involving deposits of minerals within the cells of organisms. Water from the ground, lakes, or oceans seeps into the pores of organic tissue and forms a crystal cast with deposited minerals. Crystals begin to form in the porous cell walls. This process continues on the
Permineralization
11974444
concentrated of these three minerals. The main commercial mine on Greenland's west coast closed in 1987, and most cryolite is now synthesized. Other minerals such as topaz contain fluorine. Fluorides, unlike other halides, are insoluble and do not occur in commercially favorable concentrations in saline waters. Trace quantities of organofluorines of uncertain origin have been detected in volcanic eruptions and geothermal springs. The existence of gaseous fluorine in crystals, suggested by the smell of crushed antozonite, is contentious; a 2012 study reported the presence of 0.04% by weight in antozonite, attributing these inclusions to radiation from the presence of tiny
Fluorine
291520
concentrated it in the Earth’s core. The free element is not found in nature, but niobium occurs in combination with other elements in minerals. Minerals that contain niobium often also contain tantalum. Examples include columbite ((Fe,Mn)(Nb,Ta)O) and columbite–tantalite (or "coltan", (Fe,Mn)(Ta,Nb)O). Columbite–tantalite minerals (the most common species being columbite-(Fe) and tantalite-(Fe), where "-(Fe)" is the Levinson suffix informing about the prevailence of iron over other elements like manganese) are most usually found as accessory minerals in pegmatite intrusions, and in alkaline intrusive rocks. Less common are the niobates of calcium, uranium, thorium and the rare earth elements. Examples of such
Niobium
1703845
rates occur in developing countries, where 852 million people (about 15% of the population) are chronically undernourished. The report noted that Asia and Latin America have achieved reductions in rates of undernourishment that put these regions on track for achieving the Millennium Development Goal of halving the prevalence of undernourishment by 2015. The UN noted that about 2 billion people do not consume a sufficient amount of vitamins and minerals. In India, the second-most populous country in the world, 30 million people have been added to the ranks of the hungry since the mid-1990s and 46% of children are underweight.
Food security
712503
stone. Chatoyant minerals display luminous bands, which appear to move as the specimen is rotated. Such minerals are composed of parallel fibers (or contain fibrous voids or inclusions), which reflect light into a direction perpendicular to their orientation, thus forming narrow bands of light. The most famous examples are tiger's eye and cymophane, but the effect may also occur in other minerals such as aquamarine, moonstone and tourmaline. Color change is most commonly found in alexandrite, a variety of chrysoberyl gemstones. Other gems also occur in color-change varieties, including (but not limited to) sapphire, garnet, spinel. Alexandrite displays a color
Lustre (mineralogy)
20668274
contact metamorphism and associated fluids. Alteration is seen in the occurrence of marble and minerals such as vesuvianite and humite, both of which are high on fluorine. This alteration is thought to also have affected the batholith itself. Most rocks of the batholith are monzogranites but granodiorites and tonalites do also occur. The central parts of the batholith are fully grantic and include leucogranite. Grain size vary from coarse to fine and at places the rocks are porphyritic. Dykes of lamprophyre and nephelinite that occur in the region are associated to the batholith. Pegmatites and aplites, albeit not voluminous, are
Achala Batholith
28511
the lanthanides, the actinides form a family of elements with similar properties. Within the actinides, there are two overlapping groups: transuranium elements, which follow uranium in the periodic table—and transplutonium elements, which follow plutonium. Compared to the lanthanides, which (except for promethium) are found in nature in appreciable quantities, most actinides are rare. The majority of them do not even occur in nature, and of those that do, only thorium and uranium do so in more than trace quantities. The most abundant or easily synthesized actinides are uranium and thorium, followed by plutonium, americium, actinium, protactinium, neptunium, and curium. The
Actinide
14001635
or on the ability of the experimentalist to artificially enrich the molecules, under study, with such nuclides. The most abundant naturally occurring isotopes of hydrogen and phosphorus (for example) are both magnetically susceptible and readily useful for nuclear magnetic resonance spectroscopy. In contrast, carbon and nitrogen have useful isotopes but which occur only in very low natural abundance. Other limitations on sensitivity arise from the quantum-mechanical nature of the phenomenon. For quantum states separated by energy equivalent to radio frequencies, thermal energy from the environment causes the populations of the states to be close to equal. Since incoming radiation is
Nuclear magnetic resonance
2629406
usually do. In the absence of cones, limber pine can also be hard to tell from Western white pine ("P. monticola") where they occur together in the northern Rockies and the Sierra Nevada east slope. The most useful clue here is that limber pine needles are entire (smooth when rubbed gently in both directions), whereas Western white pine needles are finely serrated (feeling rough when rubbed gently from tip to base). Limber pine needles are also usually shorter, long, while western white pine needles are , though the ranges overlap. Limber pine is susceptible to white pine blister rust, caused
Pinus flexilis
2170894
Bladder stone A bladder stone is a stone found in the urinary bladder. Bladder stones are small mineral deposits that can form in the bladder. In most cases bladder stones develop when the urine becomes very concentrated or when one is dehydrated. This allows for minerals, such as calcium or magnesium salts, to crystallize and form stones. Bladder stones vary in number, size and consistency. In some cases bladder stones do not cause any symptoms and are discovered as an incidental finding on a plain radiograph. However, when symptoms do occur, these may include severe lower abdominal and back pain,
Bladder stone
3377308
matter and energy, and especially of temperature. It can be formulated in a variety of interesting and important ways. It implies the existence of a quantity called the entropy of a thermodynamic system. In terms of this quantity it implies that The second law is applicable to a wide variety of processes, reversible and irreversible. All natural processes are irreversible. Reversible processes are a useful and convenient theoretical fiction, but do not occur in nature. A prime example of irreversibility is in the transfer of heat by conduction or radiation. It was known long before the discovery of the notion
Laws of thermodynamics
14749395
actually works, by conflating its surface appearance with its real nature. Its generalities "seem" to explain it, but in reality they do not. The theory is therefore (ultimately) "arbitrary". Either things are studied in isolation from the total context in which they occur, or generalizations are formed which leave essential bits out. Such distortion can certainly be ideologically useful to justify an economic system, position or policy as a good thing, but it can become a hindrance to understanding. Abstractly, the masking processes specific to capitalist society mediate and reconcile social contradictions, which arise from three main sources: In "The
Character mask
14675356
the ground is called magma. When magma sits in underground chambers, slowly cooling over thousands of years, heavier elements sink. These elements, including copper, chromium, iron, and nickel become concentrated at the bottom. When magma is hot, many elements are free to move. As cooling proceeds, the elements bind with each other to form chemical compounds or minerals. Because some elements do not bond easily to form minerals, they exist freely after nearly all the other elements have bonded into compounds or minerals. The remaining elements are called incompatible elements. Some of them are quite useful to humans. Some examples
Ore resources on Mars
16715074
and mercury, occur chiefly as sulfide and sulfosalt minerals. Examples of primary minerals formed in this way include the sulfide minerals pyrite (FeS), galena (PbS), sphalerite (ZnS), and chalcopyrite (CuFeS). The word hypogene is derived from the Greek "hypo-" meaning "under" and "-gene" meaning "born" or "produced". The terms "hypogene" and "supergene" refer to the depth at which they occur. Hypogene In ore deposit geology, hypogene processes occur deep below the earth's surface, and tend to form deposits of primary minerals, as opposed to supergene processes that occur at or near the surface, and tend to form secondary minerals. At
Hypogene
15408968
precision. It is important to note that data in tables found on various websites should be reverified periodically with available US Naval Observatory data, as well as compared against other reputable solunar data providers. Inconsistencies abound due to the complex nature of the astrophysics computations and overlooked associated anomalies-checking that are required to produce useful results. Moon transits which do not occur for more than a day, or associated times being off more than a few minutes are indications of a fundamental issue for a given position and should be suspect. All data providers should be verified before assuming data
Solunar theory
197055
by mass action due to the precipitation of the insoluble salt. Iodine is the least abundant of the stable halogens, comprising only 0.46 parts per million of Earth's crustal rocks (compare: fluorine 544 ppm, chlorine 126 ppm, bromine 2.5 ppm). Among the eighty-four elements which occur in significant quantities (elements 1–42, 44–60, 62–83, and 90–92), it ranks sixty-first in abundance. Iodide minerals are rare, and most deposits that are concentrated enough for economical extraction are iodate minerals instead. Examples include lautarite, Ca(IO), and dietzeite, 7Ca(IO)·8CaCrO. These are the minerals that occur as trace impurities in the caliche, found in Chile,
Iodine
10501116
Layered double hydroxides Layered double hydroxides (LDH) are a class of ionic solids characterized by a layered structure with the generic layer sequence [AcB Z AcB], where c represents layers of metal cations, A and B are layers of hydroxide () anions, and Z are layers of other anions and neutral molecules (such as water). Lateral offsets between the layers may result in longer repeating periods. The intercalated anions (Z) are weakly bound, often exchangeable; their intercalation properties have scientific and commercial interest. LDHs occur in nature as minerals, as byproducts of metabolism of certain bacteria, and also unintentionally in
Layered double hydroxides
45683
Barium Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Its hydroxide, known in pre-modern times as baryta, does not occur as a mineral, but can be prepared by heating barium carbonate. The most common naturally occurring minerals of barium are barite (now called baryte) (barium sulfate, BaSO) and witherite (barium carbonate, BaCO), both insoluble in water. The name "barium" originates from the alchemical derivative
Barium
18367827
Orthosilicate In chemistry, orthosilicate is the anion , or any of its salts and esters. It is one of the silicate anions. It is occasionally called the silicon tetroxide anion or group. Orthosilicate salts, like sodium orthosilicate, are stable, and occur widely in nature as silicate minerals, being the defining feature of the nesosilicates. Olivine, a magnesium or iron(II) orthosilicate, is the most abundant mineral in the Earth's mantle. The orthosilicate anion is a strong base, the conjugate base of the extremely weak orthosilicic acid (p"K" = 13.2 at 25 °C). This equilibrium is difficult to study since the acid
Orthosilicate
14656131
two competing processes of disproportionation (to and ) and decomposition (to and ) that the liberated diimide can also undergo. Unfortunately, this means that in the case of alkyne reduction, over-reduction to the alkane can occur resulting in diminished yields where the "cis" alkene is the desired product. A variety of methods for the generation of diimide exist. The most synthetically useful methods are: Procedures (particularly those employing air as an oxidant) are typically straightforward and do not require special handling techniques. Acetic acid-O-"d" (1.2 g) was slowly added dropwise into a solution of the carboxylic acid starting material (200
Reductions with diimide
18105927
argillite (a sedimentary rock); it is prized for a beautiful blue fluorescence under ultraviolet light. Other PAC compounds appearing as minerals include fluorene as kratochvilite; and anthracene as ravatite. Others are mixtures: curtisite contains several PAH compounds, including dibenzofluorine, picene, and chrysene, while the most common components of idrialite are tribenzofluorenes. One theory for their formation involves burial of PAH compounds until they reach a temperature where pyrolisis can occur, followed by hydrothermal transport towards the surface, during which the composition of minerals that precipitate out depends on the temperature. A salt of an organic acid is a compound in
Organic mineral
6727993
like UCl are better described with the covalent bond than an ionic bond. Minerals containing the uranous ion are more subdued in colour, typically brown or black, and occur in reducing environments. Common uranous minerals include: uraninite; pitchblende (a crystalline variant of uraninite); and coffinite "(Smith,Hutchinson and Blackwell, 1984)" Uranous Uranous is the chemical term for the reduced tetrapositive cation of uranium that exhibits the valence U. It is one of the two common ionic states of uranium found in nature, the other being the oxidised hexapositive ion called uranyl. Uranous compounds are usually unstable; they revert to the oxidised
Uranous
252982
the wolframite series of manganese-rich hübnerite and iron-rich ferberite. Chemical substitution and coordination polyhedra explain this common feature of minerals. In nature, minerals are not pure substances, and are contaminated by whatever other elements are present in the given chemical system. As a result, it is possible for one element to be substituted for another. Chemical substitution will occur between ions of a similar size and charge; for example, K will not substitute for Si because of chemical and structural incompatibilities caused by a big difference in size and charge. A common example of chemical substitution is that of Si
Mineral
9246112
Geothermobarometry Geothermobarometry is the science of measuring the previous pressure and temperature history of a metamorphic or intrusive igneous rocks. Geothermobarometry is a combination of "geobarometry", where a pressure of mineral formation is resolved, and "geothermometry" where a temperature of formation is resolved. Geothermobarometry relies upon understanding the temperature and pressure of the formation of minerals within metamorphic and igneous rocks, and is particularly useful in metamorphic rocks. There are several methods of measuring the temperature or pressure of mineral formation relying on chemical equilibrium between metamorphic minerals or by measuring the chemical composition of individual minerals. Thermobarometry relies upon
Geothermobarometry
8652296
for electrolytic manganese dioxide. Alternatively oxidation of manganese sulfate with potassium permanganate yields the so-called chemical manganese dioxide (CMD). These materials, especially EMD, are used in dry-cell batteries. Manganese(II) sulfate minerals are very rare in the nature and always occur as hydrates. The monohydrate is called szmikite; tetrahydrate = ilesite; hexahydrate (the most rare) = chvaleticeite; pentahydrate = jôkokuite; heptahydrate = mallardite. Manganese(II) sulfate Manganese(II) sulfate usually refers to the inorganic compound with the formula MnSO·HO. This pale pink deliquescent solid is a commercially significant manganese(II) salt. Approximately 260 thousand tonnes of manganese(II) sulfate were produced worldwide in 2005. It
Manganese(II) sulfate
7558938
economic concentrations of the minerals. This factor can be qualitatively or quantitatively measured through the ZTR index. The heavy minerals within the source sediments attain an economic concentration by accumulation within low-energy environments within streams and most usually on beaches. In beach placer deposits the lowest energy zone on the beach is the swash zone, where turbulent surf washes up on the beach face and loses energy. In this zone, heavier grains accumulate because they are denser than the quartz grains they occur with and become stranded. It is for this reason that beach placer deposits are often referred to
Heavy mineral sands ore deposits
11245801
or otherwise if property features are incorrectly entered. AVMs remove the human element from the valuation process and rely on computer automation so as to remove human bias and subjectivity. AVMs are particularly useful in assessing the value of a property portfolio. Using an automated model can also be useful for valuing an individual property where the provider can deliver a suitable level of accuracy. The disadvantages are that they do not take into account the property condition, as a physical inspection of the property does not occur and therefore the valuation produced assumes an average condition which may not
Automated valuation model
10766544
the EU, no matter where they originate. On August 10, 2018 The European Commission published their non-binding guidelines for the identification of conflict-affected and high-risk areas and other supply chain risks under Regulation (EU) 2017/821 of the European Parliament and of the Council. Increases in business process outsourcing to globally dispersed production facilities means that social problems and human rights violations are no longer only an organization matter, but also often occur in companies’ supply chains, and challenge for supply chain managers. Besides the harm conflict minerals do where they are produced, human rights violations also raise an enormous risk
Conflict resource
15821727
North-East of the European Russia. The reserve is mostly covered by forests, which are siberian fir (72.5%), pine (16%), birch (7%) and larch (4.6%). Most of the birch forests occupy the area where the woods previously burnt down or were cut down. Minor areas, mostly in floodplains, are occupied by meadows. The area of the Reserve is too small, and most of the animals do not reside there permanently but migrate. Among the species which occur in the Reserve are moose, brown bear (between 15 and 20), lynx, wolverine, wolf, red fox, badger, beaver, European mink, European otter and others.
Pinega Nature Reserve
2671835
sewage sludge or fecal sludge is sanitisation or sanitization. A perfect disinfectant would also offer complete and full microbiological sterilisation, without harming humans and useful form of life, be inexpensive, and noncorrosive. However, most disinfectants are also, by nature, potentially harmful (even toxic) to humans or animals. Most modern household disinfectants contain Bitrex, an exceptionally bitter substance added to discourage ingestion, as a safety measure. Those that are used indoors should never be mixed with other cleaning products as chemical reactions can occur. The choice of disinfectant to be used depends on the particular situation. Some disinfectants have a wide
Disinfectant
4074704
minerals are relatively rare in the Solar System, though they occur extensively on Earth where water has interacted with other minerals and organic matter. Clay minerals have been detected at several locations on Mars, including Echus Chasma, Mawrth Vallis, the Memnonia quadrangle and the Elysium quadrangle. Spectrography has confirmed their presence on asteroids including the dwarf planet Ceres and Tempel 1 as well as Jupiter's moon Europa. Clay minerals can be classified as 1:1 or 2:1, this originates because they are fundamentally built of tetrahedral silicate sheets and octahedral hydroxide sheets, as described in the structure section below. A 1:1
Clay minerals
484946
specific surface area and its unbalanced negative electric charges, clay is the most active mineral component of soil. It is a colloidal and most often a crystalline material. In soils, clay is a soil textural class and is defined in a physical sense as any mineral particle less than in effective diameter. Many soil minerals, such as gypsum, carbonates, or quartz, are small enough to be classified as clay based on their physical size, but chemically they do not afford the same utility as do mineralogically-defined clay minerals. Chemically, clay minerals are a range of phyllosilicate minerals with certain reactive
Soil
9394175
feldspar ophitically; less commonly iron oxides and sphene do so. In peridotites the "lustre-mottled" structure arises from pyroxene or hornblende enveloping olivine in the same manner. In these cases no crystallographic relation exists between the two minerals (enclosing and enclosed). Poikilitic Poikilitic texture refers to igneous rocks where large component crystals contain smaller crystals of other minerals within them. In poikilitic rocks, the contained smaller crystals are termed 'chadacrysts' and the larger phenocrysts are termed 'oikocrysts'. A poikilitic texture is most easily observed in petrographic thin sections. In some rocks there seem to be little tendency for the minerals to
Poikilitic
242814
"hard to get at," element 66, dysprosium was similarly named; lanthanum itself is named after a word for "hidden." The elements 57 (La) to 71 (Lu) are very similar chemically to one another and frequently occur together in nature, often anywhere from three to all 15 of the lanthanides (along with yttrium as a 16th) occur in minerals such as samarskite, monazite and many others which can also contain the other two group 3 elements as well as thorium and occasionally other actinides as well. A majority of the rare earths were discovered at the same mine in Ytterby, Sweden
Lanthanide
15739358
was subsequently filled with sediments from submarine fan systems in the area, although most of the accreted sediments consist of coarse terrestrial clastics. In Arctic regions, natural gas hydrate deposits mostly occur in sand-rich units in association with permafrost. In contrast, gas hydrates in a marine environment tend to occur in continental margin sediments consisting primarily of fine-grained clay minerals and organic debris, which has settled onto the seafloor. They appear to be a very common constituent, filling spaces between the grains and within cracks and fissures in sediments on deepwater continental shelves where the temperature and pressure conditions are
Nankai Trough gas hydrate site
268664
predicts that thousands more mineral species may await discovery or have formed and then been lost to erosion, burial or other processes. This implies a role of chance in the formation of rare minerals occur. In another use of big data sets, network theory was applied to a dataset of carbon minerals, revealing new patterns in their diversity and distribution. The analysis can show which minerals tend to coexist and what conditions (geological, physical, chemical and biological) are associated with them. This information can be used to predict where to look for new deposits and even new mineral species. Minerals
Mineralogy
540808
Some fluorine may be replaced by the chloride anion. Fluorite is a widely occurring mineral that occurs globally with significant deposits in over 9,000 areas. It may occur as a vein deposit, especially with metallic minerals, where it often forms a part of the gangue (the surrounding "host-rock" in which valuable minerals occur) and may be associated with galena, sphalerite, barite, quartz, and calcite. It is a common mineral in deposits of hydrothermal origin and has been noted as a primary mineral in granites and other igneous rocks and as a common minor constituent of dolostone and limestone. The world
Fluorite
9871549
the soil grains affects the soil strength. The residual strength occurs for some soils where the shape of the particles that make up the soil become aligned during shearing (forming a slickenside), resulting in reduced resistance to continued shearing (further strain softening). This is particularly true for most clays that comprise plate-like minerals, but is also observed in some granular soils with more elongate shaped grains. Clays that do not have plate-like minerals (like allophanic clays) do not tend to exhibit residual strengths. Use in practice: If one is to adopt critical state theory and take c' = 0; formula_1
Shear strength (soil)
15070118
environments. The central vowels do not occur in open syllables and do not occur with final approximants . The vowels seem to occur rarely with the final nasals . The incidence of final nasal consonants is very low, however, and it is not possible to conclusively state this as a restriction. With regard to approximants, only can occur with a final . do not occur with a final . The diphthong cannot combine with a final approximant and this is probably due to the vocalic nature of the approximants that would violate the syllable patterns. Unvoiced stops are characteristically unaspirated,
Kensiu language
553166
Ischia, near Naples, Hungary, etc. Andesitic tuffs are exceedingly common. They occur along the whole chain of the Cordilleras and Andes, in the West Indies, New Zealand, Japan, etc. In the Lake district, North Wales, Lorne, the Pentland Hills, the Cheviots, and many other districts of Great Britain, ancient rocks of exactly similar nature are abundant. In color, they are red or brown; their scoriae fragments are of all sizes from huge blocks down to minute granular dust. The cavities are filled with many secondary minerals, such as calcite, chlorite, quartz, epidote, or chalcedony; in microscopic sections, though, the nature
Tuff
1776317
of the material. Too much martensite leaves steel brittle; too little leaves it soft. Martensite Martensite is named after the German Adolf Martens (1850–1914). The term most commonly refers to a very hard form of steel crystalline structure, but can also refer to any crystal structure that is formed by diffusionless transformation. Martensite includes a class of hard minerals that occur as lath- or plate-shaped crystal grains. Martensite is formed in carbon steels by the rapid cooling (quenching) of the austenite form of iron at such a high rate that carbon atoms do not have time to diffuse out of
Martensite
19366155
rhodizite, and spodumene. The main facts about schiavinatoite's structure: Schiavinatoite Schiavinatoite is a very rare mineral, a natural niobium borate of the formula (Nb,Ta)BO. Schiavinatoite is classified as monoborate. It contains tetrahedral borate anion instead of planar BO group, which is more common among minerals. Schiavinatoite is one of the most simple niobium minerals. It forms a solid solution with its tantalum-analogue, béhierite. Both minerals possess zircon-type structure (tetragonal, space group "I"4/"amd") and occur in pegmatites. Schiavinatoite and nioboholtite are minerals with essential niobium and boron. Schiavinatoite was detected in miaroles of a pegmatite at Antsongombato, Madagascar. It coexists with
Schiavinatoite
19366154
Schiavinatoite Schiavinatoite is a very rare mineral, a natural niobium borate of the formula (Nb,Ta)BO. Schiavinatoite is classified as monoborate. It contains tetrahedral borate anion instead of planar BO group, which is more common among minerals. Schiavinatoite is one of the most simple niobium minerals. It forms a solid solution with its tantalum-analogue, béhierite. Both minerals possess zircon-type structure (tetragonal, space group "I"4/"amd") and occur in pegmatites. Schiavinatoite and nioboholtite are minerals with essential niobium and boron. Schiavinatoite was detected in miaroles of a pegmatite at Antsongombato, Madagascar. It coexists with an apatite-group mineral, béhierite, danburite, elbaite–liddicoatite, feldspar, pollucite, quartz,
Schiavinatoite
7255830
Tantalum pentoxide Tantalum pentoxide, also known as tantalum(V) oxide, is the inorganic compound with the formula . It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid. is an inert material with a high refractive index and low absorption (i.e. colourless), which makes it useful for coatings. It is also extensively used in the production of capacitors, due to its high dielectric constant. Tantalum occurs in the minerals tantalite and columbite (columbium being an archaic name for niobium), which occur in pegmatites, an igneous rock formation. Mixtures of columbite and
Tantalum pentoxide
5406808
which contain the industrially useful elements titanium and zirconium. These minerals typically occur combined with ordinary sand, then are separated in water by virtue of their different densities, before the sand is redeposited. Sand mining is a direct cause of erosion, and impacts the local wildlife. Various animals depend on sandy beaches for nesting clutches, and mining has led to the near extinction of gharials (a species of crocodile) in India. Disturbance of underwater and coastal sand causes turbidity in the water, which is harmful for organisms like coral that need sunlight. It can also destroy fisheries, financially harming their
Sand mining
475200
However, when dry, clay becomes firm and when fired in a kiln, permanent physical and chemical changes occur. These changes convert the clay into a ceramic material. Because of these properties, clay is used for making pottery, both utilitarian and decorative, and construction products, such as bricks, wall and floor tiles. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware, and porcelain. Prehistoric humans discovered the useful properties of clay. Some of the earliest pottery shards recovered are from central Honshu, Japan. They are associated with the Jōmon culture and deposits
Clay
3259580
of virotherapy, where oncolytic viruses are used to treat diseases; viruses can increase metabolism, reduce anti-tumor immunity and disorganize vasculature. Talimogene laherparepvec (T-VEC) (which is a herpes simplex virus type 1–derived oncolytic immunotherapy), was shown to be useful against metastatic melanoma in 2015 with an increased survival of 4.4 months. Melanoma Melanoma, also known as malignant melanoma, is a type of cancer that develops from the pigment-containing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye. In women, they most commonly occur on the legs, while in men they
Melanoma
3498455
– the obsessional neurotic being especially prone to the technique of displacement onto the minute. When two or more displacements occurs towards the same idea, the phenomenon is called condensation (from the German "Verdichtung"). Among Freud's mainstream followers, Otto Fenichel highlighted the displacement of affect, either through postponement or by redirection, or both. More broadly, he considered that "in part the paths of displacement depend on the nature of the drives that are warded off". Eric Berne in his first, psychoanalytic work, maintained that "some of the most interesting and socially useful displacements of libido occur when both the aim
Displacement (psychology)
1776309
Martensite Martensite is named after the German Adolf Martens (1850–1914). The term most commonly refers to a very hard form of steel crystalline structure, but can also refer to any crystal structure that is formed by diffusionless transformation. Martensite includes a class of hard minerals that occur as lath- or plate-shaped crystal grains. Martensite is formed in carbon steels by the rapid cooling (quenching) of the austenite form of iron at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure in large enough quantities to form cementite (FeC). Austenite is γ-Fe,
Martensite
19763748
Primary minerals A primary mineral is any mineral formed during the original crystallization of the host igneous primary rock and includes the essential mineral(s) used to classify the rock along with any accessory minerals. In ore deposit geology, hypogene processes occur deep below the earth's surface, and tend to form deposits of primary minerals, as opposed to supergene processes that occur at or near the surface, and tend to form secondary minerals. The elemental and mineralogical composition of primary rocks is determined by the chemical composition of the volcanic or magmatic flow from which it is formed. Extrusive rocks (such
Primary minerals
12143394
Indian, and Atlantic Oceans. They occur on the coastlines of countries in this range, although are most prolific in the Indo-Pacific region, having high species densities around Southeast Asia, Indonesia, and northern Australia. Most species are coastal in nature, inhabiting continental shelf marine environments including reefs, bays, sandflats, lagoons, and even estuaries. The "Carangoides" species are mostly schooling in nature, becoming more solitary with age. They are all predatory, taking a variety of fish, cephalopods, and crustaceans. Like all of the Carangidae, they are oviparous, do not guard their eggs, and (if known) display differing reproductive traits and timing between
Carangoides
14630320
rainfall is at Wingham. The most obvious mammal species in the rainforest is the grey-headed flying fox. Many other species of bats occur here too. Noteworthy birds occurring here include the osprey, green catbird, wompoo fruit-dove and brush turkey. Nocturnal gliders and possums occur in the rainforest, as do many species of reptiles, such as the land mullet. The reserve contains 76 species of trees. Most evident in Wingham Brush are the large Moreton Bay figs. Another very common plant is the giant stinging tree. The largest known blush walnut was measured at 37 metres tall, with a base of
Wingham Brush Nature Reserve
9918765
Streak (mineralogy) The streak of a mineral is the color of the powder produced when it is dragged across an un-weathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a more consistent characteristic color, and is thus an important diagnostic tool in mineral identification. If no streak seems to be made, the mineral's streak is said to be white or colorless. Streak is particularly important as a diagnostic for opaque and colored materials. It is less useful for silicate minerals, most of which have a
Streak (mineralogy)
17834208
of graph, the symbols size or shape varies with the corresponding transition probabilities. Transitions that occur within a set of sequences can also be depicted using a network-like diagram called a "state transition diagram", which displays elements as nodes in a network. This way, relationships between elements can be emphasized using graphical aids, such as by adjusting the thickness of lines between states. Transition plots and state transition diagrams are useful for depicting patterns of first-order (Markovian) transitions. They do not provide information about when transitions occur or overall sequence patterns. One visual aid that is useful in both of
Social sequence analysis
242817
which vary in content of yttrium, cerium, and lanthanum in a particular as well as varying amounts of the others. Other lanthanide/rare earth minerals include bastnäsite, florencite, chernovite, perovskite, xenotime, cerite, gadolinite, lanthanite, fergusonite, polycrase, blomstrandine, håleniusite, miserite, loparite, lepersonnite, euxenite, all of which have a range of relative element concentration and may have the symbol of a predominating one such as monazite-ce; group 3 elements do not occur as native element minerals in the fashion of gold, silver, tantalum and many others on earth but may in lunar regolith. Very rare cerium, lanthanum, and presumably other lanthanide/group 3 halides,
Lanthanide
6733843
forms an intersection lineation. This intersection lineation, L may approximate the plunge of F2 interference folds. The initial impact of a crenulation foliation may be cryptic, microscopic growth of new minerals at an angle to previous foliations. This may occur only in certain compositions of the rocks which favor growth of minerals under the P-T conditions at that time. In more brittle conditions, especially in highly micaceous rocks, a crenulation may appear as "'kink bands", where S1 foliations are kinked by the S2 foliation so that the original minerals are broken or deformed. This may not result in new mineral
Crenulation
14452079
Peak minerals Peak minerals marks the point in time when the largest production of a mineral will occur in an area, with production declining in subsequent years. While most mineral resources will not be exhausted in the near future, global extraction and production is becoming more challenging. Miners have found ways over time to extract deeper and lower grade ores with lower production costs. More than anything else, declining average ore grades are indicative of ongoing technological shifts that have enabled inclusion of more 'complex' processing – in social and environmental terms "as well as" economic – and structural changes
Peak minerals
9715306
These include calcium, phosphorus, sodium, potassium, and chloride, and are commonly found in most good-quality feeds. Horses also need trace minerals such as magnesium, selenium, copper, zinc, and iodine. Normally, if adult animals at maintenance levels are consuming fresh hay or are on pasture, they will receive adequate amounts of minerals in their diet, with the exception of sodium chloride (salt), which needs to be provided, preferably free choice. Some pastures are deficient in certain trace minerals, including selenium, zinc, and copper, and in such situations, health problems, including deficiency diseases, may occur if horses' trace mineral intake is not
Equine nutrition
6331001
for the deposits at Olduvai Gorge. A number of datable minerals occur as common detrital grains in sandstones, and if the strata have not been buried too deeply, these minerals grains retain information about the source rock. Fission track analysis of these minerals provides information about the thermal evolution of the source rocks and therefore can be used to understand provenance and the evolution of mountain belts that shed the sediment. This technique of detrital analysis is most commonly applied to zircon because it is very common and robust in the sedimentary system, and in addition it has a relatively
Fission track dating
1978465
convergent plate margins but may also occur in other tectonic settings. Intermediate volcanic rocks are created via several processes: To achieve andesitic composition via fractional crystallization, a basaltic magma must crystallize specific minerals that are then removed from the melt. This removal can take place in a variety of ways, but most commonly this occurs by crystal settling. The first minerals to crystallize and be removed from a basaltic parent are olivines and amphiboles. These mafic minerals settle out of the magma, forming mafic cumulates. There is geophysical evidence from several arcs that large layers of mafic cumulates lie at
Andesite
1068168
temperature is increased to about . In most cases the mineral natron will form together with some amount of nahcolite (sodium bicarbonate), resulting in salt mixtures like the historical natron. Otherwise, the minerals trona or thermonatrite and nahcolite are commonly formed. As the evaporation of a salt lake will occur over geological time spans, during which also part or all of the salt beds might redissolve and recrystallize, deposits of sodium carbonate can be composed of layers of all these minerals. The following list may include geographical sources of either natron or other hydrated sodium carbonate minerals: Natron Natron is
Natron
3114406
copper powder instead of copper chloride or copper bromide. But this must be done in the presence of HCl and HBr respectively. Aryl halides occur widely in nature, most commonly produced by marine organisms that utilize the chloride and bromide in ocean waters. Chlorinated and brominated aromatic compounds are also numerous, e.g. derivatives of tyrosine, tryptophan, and various pyrrole derivatives. Some of these naturally occurring aryl halides exhibit useful medicinal properties. The C-X distances for aryl halides follow the expected trend. These distances for fluorobenzene, chlorobenzene, bromobenzene, and methyl 4-iodobenzoate are 135.6(4), 173.90(23), 189.8(1), and 209.9 pm, respectively. Unlike typical
Aryl halide
2117877
into dry watersheds where the water evaporates, leaving a high concentration of minerals and other inflow erosion products. Over time this input of erosion products can cause the endorheic lake to become relatively saline (a "salt lake"). Since the main outflow pathways of these lakes are chiefly through evaporation and seepage, endorheic lakes are usually more sensitive to environmental pollutant inputs than water bodies that have access to oceans, as pollution can be trapped in them and accumulate over time. Endorheic regions can occur in any climate but are most commonly found in desert locations. In areas where rainfall is
Endorheic basin
16504862
hyperbaric environment. Thorough planning and preparation can help to minimize unanticipated interactions, and effective coping skills may be necessary to control interactions when they occur. Psychological tests? The simplistic statement that most diving accidents are due to diver error does not address the underlying reasons for the diver making the mistake. Errors are inherent in human nature, and it is more useful to consider all levels of influence on the behaviour of the diver as this may throw light on the reasons why the same errors are repeated so often. Analyses of aviation accidents show that 60 to 80% of
Human factors in diving safety
13940361
"On the Nature of Man" gives first hand accounts and explanations of individual medical cases. For example, dysentery and nosebleeds occur in the spring and summer because this is when the blood is at its hottest. Hippocrates concludes that the degree of damage a given disease can do to a person depends on its nature. The most serious of illnesses are those that affect the strongest part of the body. If the strongest part of the body is affected, then the weak parts are easily affected and may cause death. However, if a disease starts in a weak area of
On the Nature of Man
4451851
bharal, together with density-dependent forage limitation, results in resource competition and a decline in bharal density. Where they overlap, they are the favored prey of snow leopards and leopards, with a few lambs falling prey to foxes or eagles. The bharal is categorised as Least Concern by the International Union for Conservation of Nature and Natural Resources (IUCN). The population faces two threats: poaching for meat and competition with livestock. Poaching, however, is uncommon due to the unsuitable conditions of its habitat. Similarly, livestock do not generally frequent the mountainous regions where bharal occur; even if they do coexist no
Bharal
20914988
mass removal, exhumation (an isostatic-uplifting process which deep-seated rock is brought to the land surface) occurs and hence, replenishes materials for on-going denudation. Thus, the dynamic equilibrium system between denudation and exhumation further facilitates the development of thicker weathering profile as well as the accumulation of REEs. In regolith-hosted rare earth element deposits, rare earth elements ores do not exist as free ions. Instead, they physically adhere on clay minerals as clay-REE complex or chemically bond with REE-hosting minerals. Exchangeable phase (i.e. Clay-REE) accounts for 60-90% of the total REE content in the deposits. In this phase, REEs occur as
Regolith-hosted rare earth element deposits
14449342
titanium, iron, tin, aluminium and manganese, which remain during the course of weathering. Quartz is the most abundant relic mineral from the parent rock. Laterites vary significantly according to their location, climate and depth. The main host minerals for nickel and cobalt can be either iron oxides, clay minerals or manganese oxides. Iron oxides are derived from mafic igneous rocks and other iron-rich rocks; bauxites are derived from granitic igneous rock and other iron-poor rocks. Nickel laterites occur in zones of the earth which experienced prolonged tropical weathering of ultramafic rocks containing the ferro-magnesian minerals olivine, pyroxene, and amphibole. Yves
Laterite