Fluorite with Calcite

specimen number:
2312144

location:
Denton Mine, Hardin Co., Illinois, USA

description:
Deep purple to Amber lustrous and mostly gemmy crystals of fluorite measuring to 2.5 cm in size across the top of matrix. Small crystals of calcite are present. This would exhibit some unique crystal faces not often seen from this mining district for the species. In good condition.

The Denton Mine, located in Hardin County, Illinois, is situated within the Illinois-Kentucky Fluorspar District, a major Mississippi Valley-Type mineralized region. The geology of the area is characterized by Paleozoic sedimentary rocks, primarily faulted limestones and shales, which were intruded by late Cretaceous ultramafic dikes. Mineralization occurred when warm, fluorine-rich and metal-bearing hydrothermal fluids circulated through tectonic faults and fractures, depositing massive and crystalline fluorite alongside accessory minerals. Commercial mining operations in the district ramped up during the nineteenth and twentieth centuries to supply essential flux for the steel industry. Although active commercial extraction has largely ceased, the Denton Mine underground workings became internationally renowned among mineral collectors for producing specimens of fluorite, chalcopyrite, calcite, and barite.

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