Chalcocite

specimen number:
2133393

location:
Flambeau Mine, Rusk Co., Wisconsin, USA

description:

Fine North American classic, a loose cluster of beautiful blue iridescent crystallized chalcocite. In great condition all around.

The Flambeau mine, located near Ladysmith in Rusk County, Wisconsin, was a highly concentrated open-pit copper-gold mining operation situated within the early Proterozoic Penokean volcanic belt. Geologically, it was a volcanogenic massive sulfide (VMS) deposit, where mineral-rich hydrothermal fluids on the ancient seafloor precipitated dense layers of chalcocite, bornite, and chalcopyrite within volcanic and sedimentary rocks. Weathering over millions of years created a supergene enrichment zone, drastically increasing the copper grade near the surface. Although the deposit was discovered in 1968, strict environmental permitting delayed extraction for decades. Formal mining operations began with open-pit construction in 1991, and ore extraction ran from 1993 until the high-grade reserve was fully depleted in 1997. Following the closure, the site underwent an extensive, legally mandated reclamation project that completely backfilled the pit and restored the area into a natural woodland and grassland habitat.

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