Fluorite with Quartz

specimen number:
2092216

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

description:
Glassy gem bluish purple crystals of fluorite to 1.2 cm on edge across the top of matrix with sparkling crystals of micro quartz. Minimal cleaving present. Nice for this old locality.

The W.L. Davis-Deardorff mine (often referred to simply as the Davis-Deardorff mine), situated within the prominent Cave-in-Rock mining sub-district of Hardin County, Illinois, United States, was one of the most prolific and celebrated underground fluorspar operations in the Southern Illinois-Kentucky Fluorspar District. Geologically, this deposit is classified as a classic Mississippi Valley-type (MVT) stratiform bedding-replacement body hosted within Mississippian-age sedimentary rocks, specifically where low-temperature, mineral-rich hydrothermal solutions migrated laterally through favorable limestone strata along structural fault complexes. This geochemical process precipitated exceptional, world-class crystal linings within dissolution cavities and vugs, generating highly coveted mineral specimens of vibrant purple and multi-zoned fluorite cubes, lustrous black sphalerite, galena, barite, calcite, and highly unique overgrowths of microcrystalline quartz. Historically, the property was assembled by the Mahoning Mining Company (which later became the famous Ozark-Mahoning Company) following the death of former landowner William L. Davis, with systematic exploration leading to the formal commencement of underground mining at the combined Deardorff and W.L. Davis shafts in 1939. The complex served as an incredibly intense industrial producer of essential acid-grade fluorspar and base metals through the peak of World War II and the post-war industrial boom, earning a reputation among prominent mineralogists as the ultimate premier specimen mine of the era. Declining localized reserves and shifting corporate priorities eventually led to the permanent cessation of all underground mining extraction at the site in the early 1960s, after which the subterranean workings were completely shut down and allowed to flood.

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