Dolomite

specimen number:
2062266

location:
Ropes Gold Mine, Marquette Co., Michigan, USA

description:
A cluster of colorless blocky rhombohedral dolomite crystals. In good condition, neat locality example for the species. Collected in 1996.

The Ropes gold mine, located north of Ishpeming in Marquette County, Michigan, is historic as the only major producer of commercial gold in the state. Geologically, the deposit is hosted within an Archean greenstone belt, specifically situated in a highly sheared and altered serpentinite body surrounded by peridotite and talc-chlorite schists. Hydrothermal fluids circulating through these structural fracture zones deposited native gold, electrum, pyrite, and chalcopyrite within a complex network of quartz-tetrahedrite veins and heavily altered wall rock. Discovered by Julius Ropes in 1881, the mine began formal production in 1883 under the Ropes Gold Mining Company, utilizing a mill to process the precious metal. This initial operational period yielded over one hundred thousand ounces of gold before low ore grades and financial difficulties forced a closure in 1897. After nearly a century of inactivity, the Callahan Mining Corporation acquired and reopened the property, conducting modern underground mining and open-pit reclamation from 1985 until structural instability in the main shaft caused the permanent cessation of operations in 1989.

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