Calcite

specimen number:
8311318

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

description:

This is an outstanding example for the species and locality. Scalenohedral twinned lustrous translucent crystals of calcite to 7.0 cm in size set nicely on matrix.

The White Pine Mine, located in Ontonagon County, Michigan, was a unique and massive copper operation that differed significantly from the native copper mines of the Keweenaw Peninsula. Geologically, it targeted the Nonesuch Shale, a Mesoproterozoic sedimentary formation where copper mineralization occurs primarily as chalcocite (copper sulfide) and finely disseminated native copper within siltstones and shales. This stratiform deposit formed in a lacustrine or estuarine environment approximately 1.1 billion years ago. Historically, while small-scale mining occurred as early as the 1880s and 1910s, the modern era began in 1952 when the Copper Range Company developed the site into a major industrial complex. The mine utilized room-and-pillar underground methods and was a pillar of the regional economy until its closure in 1995 due to environmental and economic factors. During its peak, it was one of the largest underground copper mines in the United States, leaving a lasting impact on the history of Michigan mining.

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