Calcite with Copper

specimen number:
2062318

location:
Caledonia Mine, Ontonagon Co., Michigan, USa

description:
Fine combination piece with scalenohedral gemmy crystals of calcite to just under 1.0 cm in size set aesthetically up on a crystallized cluster of native copper. The calcite is hosting inclusions of native copper. In great condition.

The Caledonia mine, located near Mass City in Ontonagon County, Michigan, was an underground native copper mining operation situated along the historic Keweenaw Peninsula copper range. Geologically, the deposit is hosted within the Paleoproterozoic Portage Lake Volcanics, a thick sequence of basaltic lava flows where hydrothermal fluids deposited native copper and associated secondary minerals within the porous, vesicular tops of the flows, specifically targeting the Evergreen amygdaloidal bed. The property was first explored and organized in 1863 by the Caledonia Mining Company, with active mining operations commencing around that time and continuing intermittently through the late nineteenth century. Production was periodically halted due to fluctuating copper prices, but the mine underwent major revivals in the mid-twentieth century and was later operated in the late twentieth and early twenty-first centuries as a commercial specimen-mining venture, providing a long-standing source of native copper and silver specimens before formal operations eventually ceased.

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