Prehnite with Copper

specimen number:
2062254

location:
Isle Royale Mine, Houghton Co., Michigan, USA

description:
A massive nodule of prehnite, this cut in half to show the interior. Native copper is present throughout.

The Isle Royale Mine in Houghton County, Michigan, was part of the historic copper mining activity of the Keweenaw Peninsula. The mine was developed in the mid 1800s to extract native copper from amygdaloidal basalt flows of the Portage Lake Lava Series. Underground shafts and drifts were driven to follow copper bearing zones within the volcanic rock. Like other mines in the region, the Isle Royale Mine produced native copper along with associated minerals such as calcite, quartz, and epidote found in cavities within the basalt. The mine contributed to the early growth of the Michigan copper mining industry during the 19th century.

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