Calcite with Fluorite

specimen number:
2312066

location:
Minerva Mine #1, Hardin Co., Illinois, USA

description:
Spiky crystals of calcite very nice across a blue and yellow fluorite crystal matrix. In good condition with very minimal cleaving present. Classic crystal habit for the species from this locality.

The Minerva Mine No. 1, located in Hardin County, Illinois, is situated within the prolific Illinois-Kentucky Fluorspar District. The local geology is characterized by faulted Paleozoic sedimentary strata, primarily limestone and sandstone, which were intruded by Late Cretaceous igneous dikes and cut by mineralizing hydrothermal fluids. These ascending warm fluids deposited large quantities of fluorite, barite, sphalerite, and galena within fault zones and bedding-replacement deposits. Commercial mining operations at the site developed during the mid-twentieth century to supply critical fluorite for steel production and chemical manufacturing. Beyond its industrial output, the mine became world-famous among mineral collectors for producing exceptional specimens of deep purple fluorite, often associated with calcite, barite, and occasionally hydrocarbons, extracted from deep underground tunnels before its eventual closure.

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