Siderite

specimen number:
2102217

location:
Eagle Mine, Gilman, Colorado, USA

description:
Lenticular crystals of siderite to 0.5 cm are in size very nice across the top of matrix with crystallized black sphalerite. This is in really good condition. Classic material for this well-known locality.

The Eagle Mine, situated in the Gilman District on the flanks of Battle Mountain in Eagle County, Colorado, was one of the most significant and long-lived zinc and silver operations in the state. Geologically, the deposit is a premier example of a carbonate-replacement system, where hydrothermal fluids replaced specific Paleozoic limestone and dolomite layers, primarily the Mississippian Leadville Limestone. These fluids created massive chimney and manto-style ore bodies containing rich concentrations of sphalerite, galena, chalcopyrite, and silver-bearing minerals, often associated with a distinct hydrothermal dolomite halo. Historically, the district saw its first claims in 1879 during the silver boom, but the town of Gilman and the Eagle Mine reached their industrial peak under the ownership of the Empire Zinc Company and later the New Jersey Zinc Company. The mine was an engineering marvel, featuring an entire underground mill built into the mountain to process ore year-round. Operations continued relatively steadily for nearly a century until the mine was officially closed in 1984 due to falling metal prices and environmental concerns. Today, Gilman is a well-known ghost town, and the Eagle Mine remains a classic locality for mineralogists, famous for its sharp pyrite crystals and fine specimens of barite and galena.

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