Fluorite with Chalcopyrite

specimen number:
2092199

location:
Minerva Mine #1, Hardin Co., Illinois, USA

description:

A gemmy beautiful blue and yellow color zoned crystal of fluorite with inclusions of chalcopyrite floating throughout. Minimal cleaving present, this is in good condition. There interesting smaller second-generation crystals along one face.

The Minerva Mine Number 1, located near Cave-in-Rock in Hardin County, Illinois, was one of the most significant and productive operations in the Illinois-Kentucky Fluorspar District. Geologically, it exploited extensive bedded-replacement deposits within the Mississippian-aged Renault and Ste. Genevieve Limestones, where fluorine-rich hydrothermal fluids replaced carbonate layers along structural horizons. The mine is legendary for its world-class mineral specimens, particularly its large, multi-colored fluorite cubes that often display spectacular color zoning in shades of yellow, purple, and blue, frequently accompanied by sharp crystals of sphalerite, barite, witherite, and benstonite. Historically, the mine began significant development in the early 1940s under the Minerva Oil Company and operated continuously for several decades, becoming the flagship operation for the Ozark-Mahoning Company in later years. The mine remained a primary producer of acid-grade fluorspar until its eventual closure in late 1995 due to global economic pressures on the domestic mining industry. Today, Minerva Number 1 is regarded by collectors as a premier locality that defined the aesthetic standards for American fluorite.

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