Chalcopyrite with Dolomite

specimen number:
2062244

location:
Florence Mine, Florence Co., Wisconsin, USA

description:
A set of two specimen showing open cavities lined with crystallized dolomite and chalcopyrite. Good locality example collected in 1994. Size provided for the larger example.

The Florence mine, situated just north of the town of Florence in Florence County, Wisconsin, was a prominent underground and open-pit iron extraction operation that anchored the western end of the historic Menominee Iron Range. Geologically, the deposit is a Precambrian sedimentary iron-formation, specifically localized within the folded, steeply dipping Riverton Iron-Formation, which consists of interbedded chert and hematite-rich layers bounded by the underlying Dunn Creek Slate. This iron-bearing sequence was subsequently concentrated into high-grade soft hematite ore bodies through secondary supergene enrichment from circulating groundwater. Historically, the iron deposit was discovered in October 1874 by explorer Hiram D. Fisher and named in 1879 to honor Florence Terry Hulst, the wife of pioneer mining engineer Nelson P. Hulst. Active mining and development began during the winter of 1879-1880, coinciding with the arrival of the Chicago and North Western Transportation Company railroad line, which enabled large-scale ore shipments to Great Lakes ports. The mine operated extensively through the late nineteenth century and into the twentieth century, reaching its peak industrial output in the 1920s before depleting its highest-grade reserves.

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