<p>Native copper (Cu) in calcite crystal (2.05 cm across at its widest) from the Precambrian of northern Michigan, USA.
</p>
<hr><p>Northern Michigan's Keweenaw Peninsula area has bedrock with Earth's highest concentration of elemental copper (Cu) in its native state.  The copper has been extensively mined, but only one active mine remains (all the easily exploited copper is now mined out).  Copper usually occurs in various late Mesoproterozoic-aged basaltic rocks and conglomerates.
</p><p>A beautiful and rare occurrence for native copper in northern Michigan is WITHIN crystals of calcite.  This is a transparent to translucent calcite crystal that easily shows the metallic orange coloration of the included native copper.
</p><p>Stratigraphy &amp; age: derived from the upper Portage Lake Volcanic Series, upper Mesoproterozoic (1.093 Ga); copper &amp; calcite mineralization age is late Mesoproterozoic (1.05 to 1.06 Ga).
</p>
Locality: Quincy Mine, city of Hancock, north of Portage Lake, Keweenaw Peninsula, Houghton County, northwestern Upper Peninsula of Michigan, USA.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/15211788872/">Native copper in calcite crystal (late Mesoproterozoic mineralization age, 1.05-1.06 Ga; Quincy Mine, Hancock, Keweenaw Peninsula, Upper Peninsula of Michigan, USA) 1</a>