Fluorite with Sphalerite, Chalcopyrite

specimen number:
2292132

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

description:
Lustrous rosy purple translucent cubic crystals of fluorite measuring to 3.0 cm on edge on matrix with crystallized sphalerite and chalcopyrite. Some chipping present as seen. From the 1980s.

The Denton mine, located near Cave-in-Rock in Hardin County, Illinois, was a major underground fluorspar mining operation within the Illinois-Kentucky Fluorspar District. Geologically, the deposit consists of Mississippi Valley-Type (MVT) mineralized bedding-replacement ore bodies hosted primarily within Mississippian-aged carbonate strata, particularly the Joppa member of the Ste. Genevieve Limestone and the Renault Limestone. Hydrothermal fluids migrating along regional faults dissolved portions of the limestone host rock and deposited massive to crystalline fluorite, often accompanied by calcite, sphalerite, galena, barite, and chalcopyrite within large open vugs. Developed and operated by the Ozark-Mahoning Company, underground mining at the site commenced with shaft sinking around 1978 and regular production beginning around 1980 using mechanized room-and-pillar extraction methods. The facility was an important regional domestic producer of acid-grade fluorspar and fine mineral specimens until economic factors and global market shifts forced the cessation of all mining and pumping operations in December 1993, leading to the permanent flooding and closure of the underground workings.

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