Freibergite
specimen number:
2273023
location:
Eagle Mine, Gilman, Eagle Co., Colorado, USA
description: The Eagle Mine, situated on the steep flanks of Battle Mountain near Gilman in Eagle County, Colorado, is a historic underground mining complex renowned as one of the state's most prolific lead-zinc-silver producers. Geologically, the massive ore bodies consist of stratabound carbonate replacement deposits, or mantos, hosted within the Mississippian Leadville Limestone, where hydrothermal fluids associated with the Colorado Mineral Belt replaced the original rock with dense sulfide mineralization. High-grade zinc and lead ores, rich in silver and copper accessory minerals, were localized in large solution-collapse breccia pipes and tabular mantos along regional faults. Following early silver discoveries in 1879, the mining camp of Gilman developed rapidly, and formal operations under the Empire Zinc Company, later the New Jersey Zinc Company, consolidated the district into the expansive Eagle Mine system. The underground operations maintained near-continuous, large-scale production through the twentieth century, extracting critical base metals for industrial and wartime use until low metal prices and high operating costs led to the permanent closure of the facility in 1984. Freibergite is a complex silver-rich sulfosalt mineral that belongs to the tennantite-tetrahedrite group, crystallizing in the isometric system. Geologically, it forms as a primary mineral within low-to-medium temperature hydrothermal vein systems, typically occurring in association with other base and precious metal sulfides like chalcopyrite, galena, sphalerite, and acanthite. The mineral is chemically characterized by high silver substitution for copper within its complex antimony-sulfide framework, making it a critical pathfinder and ore mineral for silver extraction in classic silver-lead deposits. Visually, freibergite is opaque and displays an iron-black to dark steel-gray color with a metallic luster, often appearing as granular masses or sharp tetrahedral crystals.
Semi lustrous metallic very richly crystallized freibergite across the top of matrix with pyrite. In good condition. Classic material for this Colorado locality.
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