Copper

specimen number:
2092176

location:
Keweenaw Peninsula, Michigan, USA

description:
Crystals of native copper, some very well defined in measuring to 2.0 cm in size, across the top of an epidote rich matrix. In great condition.

The Keweenaw Peninsula of Michigan is home to the largest concentration of native copper on Earth, situated within the Midcontinent Rift System. Geologically, the deposits formed approximately 1.1 billion years ago when basaltic lava flows and interbedded conglomerates were filled by copper-bearing hydrothermal fluids. This unique mineralization produced massive quantities of pure "native" metal rather than traditional copper oxides or sulfides. Historically, indigenous peoples mined the copper for thousands of years before the first modern American mining rush began in 1843. Major industrial operations, led by companies such as Calumet and Hecla, dominated the region throughout the late 19th and early 20th centuries. Production peaked during World War I, but as the mines reached extreme depths and costs increased, the industry steadily declined. Most major mines closed by the late 1960s, with the final large-scale operation, the White Pine Mine, shutting down its primary production in 1995.

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