Siderite with Sphalerite

specimen number:
2072211

location:
Eagle Mine, Gilman, Colorado, USA

description:
Lenticular crystals of siderite covering most of the top of matrix. Crystallized black sphalerite present as well. Classic Colorado specimen in good condition.

The Eagle Mine, situated on Battle Mountain near Gilman in Eagle County, Colorado, was one of the state's most productive and deep-seated mining operations. Geologically, the deposit consists of massive polymetallic replacement bodies (mantos) and veins hosted within the Mississippian Leadville Limestone, where mineralizing fluids replaced carbonate rock with rich ores of zinc, copper, silver, and gold. The mine is mineralogically famous for its exceptional specimens of pyrite, siderite, and golden barite found in large solution cavities. Historically, mining in the Gilman district began with silver discoveries in 1879, but the Eagle Mine truly flourished under the New Jersey Zinc Company, which consolidated the workings in 1915. It operated as a major industrial pillar and a company town until 1984, when falling metal prices and high costs led to its closure. Following the cessation of mining, the site was designated a Superfund site due to heavy metal contamination of the Eagle River, leading to extensive reclamation efforts that continue to define the area's modern history.

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