Fluorite with Quartz, Sphalerite

specimen number:
2292130

location:
Davis-Deardorff Mine, Hardin Co., Illinois, USA

description:
A rosy purple lustrous gemmy cubic crystal of fluorite 1.7 cm on edge set on matrix, one side of this matrix coated with sparkling crystals of quartz. Black sphalerite crystals are present as well. Slight damage present, this still in good condition and quite fine for this old locality.

The Davis-Deardorff mine, located in Hardin County, Illinois, was a notable underground mining operation situated within the famous Illinois-Kentucky Fluorspar District. Geologically, the deposit consists of both stratabound bedding-replacement ore bodies and mineralized fault veins hosted within Mississippian-aged sedimentary rocks, particularly the Fredonia Limestone member of the Ste. Genevieve Formation. Hydrothermal mineralizing fluids migrated through regional fault systems, replacing the carbonate host rock and depositing fluorite, sphalerite, galena, and barite within porous zones and open solution cavities. Mining operations at the site commenced in the early 1940s under the management of the Ozark-Mahoning Company to meet increased industrial and wartime demand for metallurgical and acid-grade fluorspar. The mine utilized underground room-and-pillar extraction methods to access the replacement deposits until the mid-1950s, when primary ore reserves at this specific shaft were depleted and production shifted to other adjacent deposits within the district.

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