Chalcocite

specimen number:
2062327

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

description:

Very fine iridescent crystal grouping of chalcocite. In good condition with slight damage along one edge of the crystal grouping only. Choice thumbnail for this American classic.

The Flambeau mine, located near Ladysmith in Rusk County, Wisconsin, is a copper-gold deposit known for producing sharp, well-crystallized specimens of chalcocite and bornite. Geologically, the deposit is a supergene-enriched volcanogenic massive sulfide (VMS) body hosted within the Paleoproterozoic Penokean volcanic island arc terrain. Low-grade primary mineralization was significantly enriched by ancient weathering processes, creating a high-grade secondary chalcocite zone in the upper portions of the deposit where copper-rich fluids precipitated excellent crystals within open fractures and cavities. Discovered in 1968 by the Kennecott Copper Corporation, commercial open-pit extraction was delayed by regulatory and environmental reviews until operations finally commenced in 1993 under the Flambeau Mining Company. The highly efficient, fully mechanized mining phase was brief, concluding in 1997 after the extraction of approximately 1.9 million tons of ore, followed by immediate and extensive environmental reclamation that completely backfilled the pit and restored the surface to a natural grassland habitat by the early 2000s.

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