Calcite with Hematite

specimen number:
2062253

location:
Bradley Mine, Dickinson Co., Michigan, USA

description:
An open pocket in a hematite matrix is line colorless crystals of calcite. In good condition. Collected in 1999.

The Bradley mine, located near Iron Mountain in Dickinson County, Michigan, was a notable open-pit and underground iron mining operation situated within the Menominee Iron Range. Geologically, the deposit is hosted within the Paleoproterozoic-age Vulcan Iron Formation, which consists of interbedded chert and iron-rich layers that underwent intense folding, faulting, and subsequent secondary enrichment by circulating groundwater. This supergene alteration leached out silica and concentrated the iron minerals into high-grade orebodies composed primarily of dense hematite and specular hematite. Historically, commercial development at the Bradley property began during the early twentieth century, with open-pit quarrying and underground shaft sinking commencing in earnest around 1912 to supply domestic blast furnaces with high-grade shipping ore. The mine was operated by the Bradley Mining Company and later managed under lease agreements by larger regional conglomerates, maintaining intermittent production through the World War I era and the subsequent decades. Commercial ore extraction at the Bradley mine property permanently concluded in the mid-twentieth century as the localized high-grade lenses reached economic exhaustion, leaving the site inactive while regional iron production shifted toward large-scale taconite pellet operations elsewhere on the range.

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