Copper

specimen number:
2062355

location:
Grand Portage Mine, Houghton Co., Michigan, USA

description:

A large crystalline native copper specimen. Collected by Ray around the year 1951.

The Grand Portage Mine, located in Houghton County within the Michigan Copper Country, was opened in 1853 during the early wave of commercial mining exploration along the Keweenaw Peninsula. Geologically, the property is situated within the Precambrian Portage Lake Lava Series, consisting of a sequence of northward-dipping basaltic lava flows and interbedded sedimentary layers that host native copper mineralization within amygdaloidal tops and fissure veins. Mineralogically, the mine produced native copper alongside associated accessory minerals typical of the district, such as native silver, quartz, calcite, and various secondary copper alteration products. Operating under primitive conditions during its early history, the venture ultimately yielded thousands of tons of refined copper before its operations were eventually consolidated into the broader Isle Royale mining tracts.

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