Pyrite

specimen number:
2102354

location:
Eagle Mine, Gilman, Colorado, USA

description:
Bright lustrous golden crystals of pyrite measuring to 2.3 cm in size across the top of matrix. Slight chipping present, this still in good condition. Classic Colorado specimen.

The Eagle mine, situated on the slopes of Battle Mountain near Gilman in Eagle County, Colorado, was one of the state's most prolific and deep underground base-metal operations. Geologically, the deposit is a classic carbonate replacement system where Mississippian-aged Leadville Limestone beds were dissolved and replaced by massive silver-lead-zinc sulfide ores, forming spectacular horizontal mantos and vertical pipe-like chimneys along major fault zones. Gold was initially discovered in the district in 1879, sparking a silver rush that led to the founding of Gilman, but as the shallow oxide veins were depleted, operations consolidated under the New Jersey Zinc Company in 1912. This ushered in a massive industrial era featuring the construction of an entire underground milling and processing plant carved directly into the granite canyon walls to handle deep sulfide ores. The Eagle mine sustained near-continuous production throughout the twentieth century, serving as a primary national supplier of zinc during World War II, until falling metal prices and high environmental operating costs led to its permanent closure in December 1984.

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