Copper

specimen number:
2242093

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

description:
Sharp crystals of native copper measuring to almost 0.5 cm in size and a branching cluster with quartz. This is in great condition.

The Cliff Mine, located near Phoenix in Keweenaw County, Michigan, was the first mine in the Lake Superior district to achieve significant commercial success by mining native copper from fissure veins. Geologically, the mine exploited the Cliff Vein, a massive vertical fissure that cut transversely through the basaltic lava flows of the Portage Lake Volcanics. Unlike most copper mines that extract small grains of metal from rock, the Cliff was famous for producing enormous masses of pure native copper, some weighing several tons, which required specialized "sand-blasting" and hand-cutting to remove. Historically, the Pittsburgh and Boston Mining Company began operations at the site in 1845, and it quickly became the first mine in the Copper Country to pay a dividend to its shareholders. The primary period of industrial mining and quarrying lasted from 1845 until 1870, during which time it was the most productive copper mine in the United States. Although various companies attempted to revive the property in the late 19th and early 20th centuries, the mine never regained its former glory.

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