Enargite with Pyrite
specimen number:
2102406
location:
Leonard Mine, Butte, Montana, USA
description: The Leonard mine, situated within the historic Butte district of Silver Bow County, Montana, was one of the premier deep underground copper mining operations in the United States. Geologically, the deposit is hosted within the late Cretaceous-aged Butte Quartz Monzonite, a massive pluton fractured by complex, intersecting fault systems that acted as conduits for rich hydrothermal fluids. These fluids extensively altered the host rock and deposited massive sulfide veins and structural horse-tail zones packed with high-grade copper ores, primarily chalcocite, enargite, and bornite. Originally located as a mining claim in 1901 by the Anaconda Copper Mining Company, formalized shaft sinking quickly developed the site into one of the largest production nodes on the Butte hill. The Leonard shaft eventually reached a depth of over thirty-five hundred feet, extracting millions of tons of ore through decades of continuous industrial activity. Deep underground operations at the Leonard mine were maintained for over seven decades until changing corporate economics and a district-wide shift toward bulk open-pit mining at the adjacent Berkeley Pit led to its permanent closure in 1974.
Metallic lustrous crystals of enargite measuring to 2.0 cm in size very rich across the top of matrix with minor pyrite. Some damage present as seen, this still a very choice hand sized specimen for this old locality.
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