Chalcocite

specimen number:
8282260

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

description:

A very fine large cluster of chalcocite crystals measuring to 1.5 cm in size. There is no attached matrix, this is crystallized completely all around. An excellent small cabinet example from this important and short-lived locality. From the mid 1990s.

The Flambeau mine, located near Ladysmith in Rusk County, Wisconsin, was a highly successful, short-term open-pit base-metal mining operation that served as a modern benchmark for environmental reclamation. Geologically, the deposit was a supergene-enriched, volcanogenic massive sulfide body hosted within the Paleoproterozoic-age Penokean volcanic belt. Long-term weathering of the original primary chalcopyrite and pyrite ore during the Mesozoic era created a remarkably rich upper secondary enrichment zone dominated by high-grade chalcocite and bornite, along with significant accessory gold and silver. Historically, the deposit was discovered in 1968 by the Kennecott Copper Corporation, sparking decades of intense regulatory debate, environmental review, and local negotiations before mining permits were ultimately granted. Actual open-pit extraction began in 1993 under the Flambeau Mining Company, a subsidiary of Kennecott, and operated swiftly for only four years until the economic ore body was completely exhausted in 1997. During its brief operational lifespan, the mine produced nearly two hundred thousand tons of copper along with substantial precious metal byproducts, after which the open pit was completely backfilled, re-contoured, and successfully returned to a natural wetland and woodland habitat that remains monitored and open to the public through 2026.

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