Pyrite

specimen number:
2102356

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

description:
Bright lustrous golden crystals of pyrite to 2.5 cm in size across the top of a massive pyrite matrix. This is in good condition. Classic specimen for this mining district.

The Butte mining district, located in Silver Bow County, Montana, earned the moniker "The Richest Hill on Earth" due to its staggeringly dense concentration of copper, zinc, lead, silver, and gold. Geologically, the district is centered on the late Cretaceous-aged Boulder Batholith, where a massive intrusion of Butte Quartz Monzonite was heavily fractured and invaded by successive waves of deeply sourced, Eocene-aged hydrothermal fluids. These events formed a complex network of massive, deep-seated fissure veins alongside extensive zones of disseminated porphyry copper mineralization, rich in chalcocite, bornite, enargite, and sphalerite. Gold and silver placer mining initially put the camp on the map in 1864, but the discovery of rich copper veins at depth sparked an unparalleled industrial boom in the late 1870s and 1880s led by legendary copper kings like Marcus Daly and William A. Clark. This activity culminated in the formation of the Anaconda Copper Mining Company, which consolidated hundreds of miles of underground deep-shaft operations. To combat rising operational costs, the district transitioned dramatically from underground shaft mining to massive open-pit quarrying with the launch of the Berkeley Pit in 1955. Underground extraction ceased entirely in 1975, and the Berkeley Pit itself was shut down in 1982 due to falling metal prices. However, active production continues today at the adjacent Continental Pit open-pit quarry, which was opened in 1980 and is currently operated by Montana Resources, carrying Butte's commercial mining history well into its second century.

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