Chalcocite with Quartz

specimen number:
2102375

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

description:

Bright lustrous metallic crystals of chalcocite across the top of a crystallized quartz matrix in good condition with very minimal micro-damage present. Quite nice for the species and this old mining district.

The Butte mining district, situated in Silver Bow County, Montana, earned international fame as The Richest Hill on Earth due to its astronomical production of copper, zinc, manganese, silver, and gold. Geologically, the district is centered on the Butte Quartz Monzonite, a major intrusive phase of the late Cretaceous-age Boulder Batholith that was subjected to intense structural fracturing and multiple stages of high-temperature hydrothermal mineralization. This activity created an extraordinarily dense network of deep-seated, complexly zoned magmatic-hydrothermal veins and massive porphyry copper systems, containing heavy concentrations of chalcocite, bornite, enargite, chalcopyrite, and sphalerite. Historically, the area began as a localized gold-placer mining camp in 1864, transitioning to underground quartz-vein silver mining in the 1870s before Marcus Daly and other copper kings recognized the immense copper potential of the Anaconda vein system in 1881. Full-scale commercial underground shaft mining grew rapidly, with hundreds of miles of deep tunnels operated by the Anaconda Copper Mining Company dominating regional production throughout the late nineteenth and early twentieth centuries. To maximize efficiency and handle declining ore grades, extraction shifted dramatically in 1955 to large-scale, highly mechanized open-pit quarrying at the massive Berkeley Pit, which operated continuously until its sudden closure due to economic factors and rising pumping costs in April 1982. Following a brief suspension, active corporate mining operations resumed in 1986 at the adjacent Continental open-pit quarry, a major copper and molybdenum operation managed by Montana Resources that continues systematic extraction, milling, and processing through 2026.

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