Pearceite with Sphalerite
specimen number:
2262061
location:
Anselmo Mine, Butte, Montana, USA
description: The Anselmo Mine, situated in the western part of the legendary Butte District in Silver Bow County, Montana, is a classic example of a hydrothermal vein deposit hosted within the Boulder Batholith. Geologically, the mine exploited steep, east-west trending veins of the Anaconda system, where mineralizing fluids deposited zinc and lead ores within quartz-monzonite country rock. Unlike the copper-rich central core of Butte, the Anselmo was a primary producer of zinc and silver, with the secondary oxidation zones yielding notable specimens of crystallized rhodochrosite and native silver. Historically, mining and quarrying activities at the site began in the late 1880s, but the mine saw its most significant development after being acquired by the Anaconda Copper Mining Company in the early 20th century. The Anselmo remained a major operational shaft for several decades, continuing through the mid-1900s before large-scale underground production in that sector of the district eventually wound down by the late 1950s. As of 2026, the iconic headframe remains a prominent part of the Butte skyline, serving as a historical landmark that represents the district's transition from copper-focused mining to complex polymetallic extraction.
Metallic platy crystals of pearceite on a chalcopyrite matrix with honey colored translucent crystals of sphalerite. Quite nice for this silver species mineral for this locality and mining district.
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