Fluorite

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An attractive cluster of purple translucent lustrous cubic crystals of fluorite measuring to 5.0 cm in size. Damage present as seen.The Southern Illinois fluorspar district, centered primarily in Hardin and Pope counties, is a historically major mining region that was the premier producer of fluorite in the United States. Geologically, the district is located within the Illinois Basin and is characterized by a complex network of faults related to the late Paleozoic Hicks Dome cryptoexplosive structure. Mineralization occurs primarily as bedding-replacement deposits in Mississippian limestones and as vein fillings along high-angle normal faults, where low-temperature hydrothermal fluids deposited fluorite alongside sphalerite, galena, barite, and calcite. Commercial mining began around 1842 and experienced major booms during World War I and World War II due to the high industrial demand for flux in steel manufacturing. Production steadily declined in the late twentieth century because of cheap foreign imports, culminating in the closure of the last active underground mine by the Hastie Mining Company in 1995, though sporadic quarrying and processing of industrial material have persisted in the district.