Bornite with Pyrite, Enargite

specimen number:
2102212

location:
Steward Mine, Butte, Montana, USA

description:
Somewhat rounded metallic crystallized bornite very rich and mostly covering the top of a pyrite crystal matrix. Minor enargite is present as well. In good condition with very minimal damage present, a superb large cabinet example for the species from this famous old locality.

The Steward Mine, located in the legendary Butte District of Silver Bow County, Montana, was one of the deepest and most productive underground operations on the Richest Hill on Earth. Geologically, the mine exploited a dense network of hydrothermal veins hosted within the Boulder Batholith, a massive Cretaceous-aged quartz monzonite intrusion. These veins, which are part of a world-class porphyry copper system, were enriched with high-grade copper sulfides like chalcocite, enargite, and bornite, along with significant silver and zinc values. Historically, the Steward was established in the late 19th century and became a cornerstone of the Anaconda Copper Mining Company's empire. Its main shaft eventually reached a staggering depth of 4400 feet, making it a critical hub for the district's complex underground drainage and ventilation systems. The mine operated nearly continuously through the peak of the Butte mining boom and the two World Wars, with major production continuing until the transition toward open-pit mining at the Berkeley Pit led to the closure of most deep underground shafts in the 1970s.

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