Pyrrhotite with Pyrite, Calcite, Quartz

specimen number:
2062213

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

description:
Metallic small crystals of pyrrhotite and pyrite in a pocket lined by crystallized calcite and quartz. Nice locality example for the species. Collected in 1995.

The Ropes gold mine, located just north of Ishpeming within Ishpeming Township of Marquette County, Michigan, United States, stands as the premier and most historically significant lode gold operation in the state of Michigan. Geologically, this unique deposit is hosted within the Paleoproterozoic-age Ishpeming Greenstone Belt, where an intricate network of quartz-carbonate veins cuts through highly sheared, hydrothermally altered serpentine and talc-chlorite schist rocks. These auriferous vein systems developed during intense Precambrian regional deformation and metamorphic dehydration events, which concentrated ascending, volatile-rich fluids that slowly precipitated native gold and electrum alongside secondary pyrite, chalcopyrite, and minor galena within the fracture networks. Historically, the deposit was discovered on May 17, 1881, by a local chemist named Julius Ropes, sparking a localized mineral rush and leading to immediate underground shaft development by the Ropes Gold and Silver Company. Regular underground mining and mercury-amalgamation milling ran continuously from 1883 until financial difficulties forced the closure of the original 15-level underground workings in 1897, though specialized operators successfully used cyanide leaching to recover additional bullion from the surface tailings dumps between 1900 and 1901. Following nearly eight decades of complete dormancy, the dramatic economic inflation of precious metals prompted the Callahan Mining Corporation to purchase the property and initiate a major corporate redevelopment project, resulting in a successful modern revival that extracted gold and silver through a deep truck decline from 1985 until low market prices and structural instabilities within the main shaft forced permanent closure in 1989.

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