Chalcocite

specimen number:
8311260

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

description:
Beautifully crystallized iridescent chalcocite without matrix. Classic material from the 1990s.

The Flambeau Mine, located near Ladysmith in Rusk County, Wisconsin, was a remarkable high-grade copper deposit that became famous for its world-class chalcocite specimens. Geologically, it was a volcanogenic massive sulfide (VMS) deposit hosted within the Precambrian rocks of the Penokean Volcanic Belt, where tectonic activity created a steeply dipping ore body. While the primary ore was chalcopyrite, a thick secondary enrichment zone formed through millions of years of weathering, concentrating copper into spectacular masses of native copper and crystallized chalcocite. The chalcocite from this locality is legendary, occurring as sharp, thick, tabular crystals with a brilliant metallic luster and occasionally a colorful iridescent tarnish. Historically, the deposit was discovered in 1968, but environmental and regulatory reviews delayed mining for decades. The Flambeau Mining Company finally operated the site as a small, high-efficiency open pit between 1991 and 1997. Despite its short lifespan, the mine produced over 180,000 tons of copper and is now a model for successful mine reclamation, with the site fully restored to a natural park and wetlands.

Questions about this specimen?
Send an email or call us: 314-341-1811.