Copper

specimen number:
8311547

location:
Phoenix Mine, Keweenaw Co., Michigan, USA

description:

A grouping of native copper crystals, these quite sharp and measuring to 2.0 cm in size. These have an excellent patina. In great condition.

The Phoenix mine, located in Keweenaw County near the northern tip of the Keweenaw Peninsula, Michigan, United States, was a historic underground native copper operation renowned for producing massive pieces of pure metal and incorporating some of the earliest exploratory workings in the Lake Superior district. Geologically, this deposit is situated within the Mesoproterozoic-age Portage Lake Volcanics of the Midcontinent Rift System, where mineralizing hydrothermal fluids filled structurally controlled fissures, faults, and cross-cutting fractures to form tabular vein deposits dominated by heavy masses of native copper and native silver alongside secondary prehnite, calcite, and quartz. Historically, organized mining at the site began in 1844 under the Lake Superior Copper Company, making it one of the first formal mining ventures in the region, which was subsequently reorganized as the Phoenix Mining Company in 1849 to exploit the famous Phoenix and Robbins veins. The operation encountered mixed success due to the erratic distribution of the massive copper blocks, which required tedious hand-chiseling to extract, leading to intermittent periods of activity and multiple shutdowns throughout the mid-to-late nineteenth century. A final major revival occurred between 1899 and 1905 when the company constructed a modern stamp mill and reopened the old underground shafts, but inadequate ore grades and high production costs forced a permanent cessation of all commercial underground extraction in 1905.

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