Calcite

specimen number:
2062239

location:
White Pine Mine, Ontonogan Co., Michigan, USA

description:
Sharp lustrous partly gemmy scalenohedral crystals of calcite in a cluster with little attached matrix. Very choice for the species from this locality. This is in good condition with just slight cleaving to one of the lesser prominent crystals.

The White Pine mine, situated near the town of White Pine in Ontonagon County, Michigan, was a massive underground mining operation that stood as one of the largest and most technologically advanced producers of copper in North America. Geologically, the deposit is a premier example of a stratiform, sediment-hosted copper system localized within the Mesoproterozoic Oronto Group, specifically targeting the organic-rich siltstones and shales of the Nonesuch Formation. Unlike the native copper deposits found further north on the Keweenaw Peninsula, the mineralization at White Pine consists primarily of finely disseminated chalcocite along with lesser amounts of native copper and native silver, which precipitated when copper-rich fluids interacted with the reducing environment of the ancient lake-bed sediments. Historically, indigenous peoples and early prospectors knew of the outcropping copper along the Mineral River, leading to minor exploration shaft-sinking between 1879 and 1881, followed by an initial period of underground production from 1915 to 1921 under Calumet and Hecla. Large-scale modern industrial development began in the early 1950s when the Copper Range Company utilized extensive room-and-pillar mining techniques and constructed a massive mill and smelter complex, with full production commencing in 1955. The mine operated continuously for over four decades, employing thousands of workers and producing billions of pounds of copper, until high operating costs and environmental challenges led to the permanent cessation of mining and smelting operations in 1995.

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