Copper

specimen number:
2062333

location:
Osceola Mine, Houghton Co., Michigan, USA

description:

Beautifully crystallized branching specimen of native copper. In terrific condition all around.

The Osceola mine, located near Calumet in Houghton County, Michigan, was a major underground copper mine that exploited the native copper deposits of the Keweenaw Peninsula. Geologically, the mine targeted both the Osceola Amygdaloid, an altered, gas-bubble-rich volcanic basalt flow top, and the nearby Calumet and Hecla conglomerate bed, where native copper precipitated within open pore spaces and fractures from deep-seated, low-temperature hydrothermal fluids. Organized in 1873, the Osceola Mining Company began active production in the late 1870s and eventually merged into the Calumet and Hecla Mining Company in 1911. The mine operated through a series of deep vertical and inclined shafts, remaining a steady producer of native copper until economic hardships during the Great Depression forced a shutdown in 1931. The underground workings were later unwatered and reopened for intermittent production during the mid-twentieth century, operating until final, permanent closure in 1968 due to a combination of labor strikes and declining ore grades.

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