Chalcocite on Chalcopyrite

specimen number:
2062219

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

description:
Fine combination piece from this well-known and long closed Wisconsin locality. Small sparkling crystals of chalcocite are scattered across the top of a somewhat iridescent botryoidal chalcopyrite crystal matrix. This is in good condition. This would have been collected by Casey Jones.

The Flambeau mine, situated just south of Ladysmith within Rusk County, Wisconsin, United States, represents a highly significant and historically successful open-pit base metal operation noted for its intense focus on high-grade copper extraction. Geologically, this deposit was a supergene-enriched volcanic-associated massive sulfide (VMS) ore body hosted within deeply deformed, Paleoproterozoic-age metavolcanic and metasedimentary rocks belonging to the Ladysmith-Rhineander volcanic complex of the Penokean volcanic belt. Long-term subaerial weathering during the Mesozoic Era deeply oxidized the upper portions of the copper-rich iron sulfide body, creating an exceptionally enriched secondary zone where descending groundwater solutions concentrated massive chalcocite and bornite ores beneath a classic gossan cap. Historically, the deposit was discovered in November 1968 by the Kennecott Copper Corporation, but extensive environmental permitting battles and regulatory reviews delayed the commencement of active open-pit quarrying and extraction until July 1993 under the corporate management of the subsidiary Flambeau Mining Company. The highly mechanized, compact open-pit operation ran continuously for four years, extracting approximately 1.9 million tons of high-grade copper ore alongside significant gold and silver byproducts before economic reserves were completely exhausted, leading to the permanent cessation of all mining activity in March 1997. Following the completion of ore removal, a comprehensive, multi-million dollar reclamation project completely backfilled the deep pit with original waste rock and lime to neutralize acidity, restoring the surface topography to its natural contours by 1998, so that through 2026, the fully reclaimed site exists entirely as a public nature park and wildlife habitat while remaining an important reference benchmark for modern environmental engineering and midwestern American industrial history.

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