Chalcocite

specimen number:
2262257

location:
Butte, Silver Bow Co., Montana, USA

description:
Good reference example for the species and classic locality, this a mass of mostly chalcocite. The specimen comes with a previous collection data card and dates to 1967.

The Butte mining district, located in Silver Bow County, Montana, is historically celebrated as one of the most prolific copper, silver, and zinc localities on Earth, earning the moniker of the Richest Hill on Earth. Geologically, this immense world-class deposit is centered on the Late Cretaceous-age Boulder Batholith, specifically hosted within the quartz monzonite of the Butte Pluton, which was shattered by thousands of intersecting fault fractures. Late-stage, metal-rich hydrothermal fluids ascended along these complex structures, generating an extensive network of zoned, high-grade epithermal and porphyry veins that precipitated massive amounts of chalcopyrite, bornite, chalcocite, enargite, and sphalerite, often accompanied by world-class quartz and rhodochrosite crystals within the quartz-carbonate gangue. Historically, mining in the district began with alluvial gold placer panning in 1864, transitioning to underground silver vein extraction in the 1870s, and exploding into a monumental industrial copper boom by the early 1880s as electrical infrastructure drove global demand. Hundreds of independent claims were consolidated during the legendary War of the Copper Kings, giving rise to the Anaconda Copper Mining Company, which oversaw hundreds of miles of deep underground workings until escalating costs and engineering shifts prompted the opening of the massive Berkeley Pit open-pit quarrying operation in 1955. Continuous, large-scale mining ran at the site for well over a century until the Anaconda Company halted all underground operations in 1975 and permanently shut down the Berkeley Pit in 1982, though modern operations resumed at the adjacent Continental Pit under Montana Resources in 1986 and continue extracting copper and molybdenum through 2026.

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