Epidote

specimen number:
2102194

location:
Calvert Pit, Beaverhead Co.,, Montana, USA

description:
A lustrous prismatic terminated crystal grouping of epidote. In good condition.

The Calvert Pit, located in the Pioneer Mountains of Beaverhead County, Montana, is a well-known locality for high-quality epidote specimens. Geologically, the site is a tungsten skarn deposit formed where the Cretaceous-aged Pioneer Batholith intruded into Paleozoic carbonate rocks, specifically the Meagher Limestone. This contact metamorphism resulted in the formation of pockets where lustrous, dark green to nearly black epidote crystals developed, often appearing as sharp, tabular prisms. Historically, the mine was operated primarily for scheelite, an ore of tungsten, with major production periods occurring during the mid-20th century, specifically between 1956 and 1961 under the Minerals Engineering Company. While industrial operations were relatively short-lived, the locality gained recognition among mineral collectors for producing some of the most distinct epidote crystals in the region, frequently associated with quartz and calcite. Today, the pit is inactive and partially flooded, but it remains a significant reference site for the study of contact metasomatic processes in the Northern Rockies.

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