Copper

specimen number:
2062160

location:
Spencer Shaft, Copper Falls Mine, Keweenaw Co., Michigan, USA

description:
Crystal grouping of well-formed native copper 1.5 cm across set on a matrix that is predominantly made up of datolite. Collected in August 1999.

The Copper Falls Mine, located near Eagle Harbor in Keweenaw County, Michigan, was one of the earliest and most significant operations in the Lake Superior copper district. Geologically, the mine exploited native copper found within both the amygdaloidal flow tops of the Portage Lake Volcanics and the Ashbed lode, a specific tuffaceous and basaltic sequence. The mineralization occurred as copper filling gas bubbles and fractures, often associated with a diverse suite of zeolites like analcime and natrolite. Historically, the property was first explored in 1845 and saw several phases of development under various companies, including the notable Copper Falls Mining Company. The mine was a pioneer in using gravity-based stamps and experienced its most productive years between 1850 and 1893. While most major underground work ceased by the late 1890s, the site remains famous among collectors for its sharp crystals of copper and rare mineral associations. Today, the ruins of the mine and its expansive poor rock piles serve as a testament to the mid-19th century mining rush on the Keweenaw Peninsula.

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