Quartz

specimen number:
2062295

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

description:
Colorless mostly gemmy crystals of quartz across the front of matrix. Minimal damage present, still a good reference quality cabinet piece for this locality and species.

The Isle Royale mine, located on the Keweenaw Peninsula in Houghton County, Michigan, was a major underground copper mining operation situated along the historic Portage Lake native copper district. Geologically, the deposit is hosted within the Keweenawan Portage Lake Volcanics, a thick sequence of Precambrian basaltic lava flows where hydrothermal solutions filled structural vesicles and fractures to precipitate pure native copper alongside epidote, quartz, and calcite within the amygdaloidal flow tops. Organized mining at the site began in 1852 under the Isle Royale Mining Company, targeting the prominent Isle Royale lode through a series of deep vertical and inclined shafts. After experiencing fluctuating production and undergoing several corporate reorganizations, the property was consolidated into the Isle Royale Copper Company in 1899, which modernized the infrastructure and operated a dedicated stamp mill on Portage Lake. The mine sustained heavy industrial production through the early twentieth century, but economic strains from the Great Depression and declining ore grades led to a complete suspension of underground operations in 1932, with brief surface reclamation work occurring during World War II before permanent abandonment.

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