Bournonite

specimen number:
8311481

location:
Viboras Mine, Potosi, Bolivia

description:
A grouping of semi lustrous twinned bournonite crystals with little matrix. In good condition.

The Viboras Mine, located in the Hayllatiri District of the Dalence Province within the Oruro Department of Bolivia, is a classic hydrothermal vein deposit situated in the Eastern Cordillera. Geologically, the mine consists of mineralized tin and silver veins hosted within Silurian sedimentary rocks, specifically quartzites and shales, which underwent mineralization during the Miocene epoch. The locality is highly prized by collectors for its exceptional specimens of twinned bournonite, which frequently occur as sharp, metallic-gray crystals in the iconic "cogwheel" twin habit. Historically, mining and quarrying at the site have primarily targeted cassiterite and silver ores, with formal industrial activity peaking during the 20th century under the administration of the Corporacion Minera de Bolivia (COMIBOL). While large-scale production has fluctuated due to economic shifts in the Bolivian tin belt, the mine has remained a steady producer of high-quality sulfide specimens for decades. As of 2026, the Viboras Mine is recognized as a premier South American locality for its unique crystallization and historical role in the regional mining industry.

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