Fluorite with Calcite

specimen number:
2242086

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

description:
A large cluster of beautiful light blue to yellow gemmy lustrous crystals of fluorite, small crystals of spiky calcite scattered throughout. This is in really good condition with just slight cleaving to some of the calcite crystals. Quite attractive when backlit, this is really fine.

The Minerva No. 1 Mine, located near Cave-in-Rock in Hardin County, Illinois, was a premier operation within the world-famous Illinois-Kentucky Fluorspar District. Geologically, the deposit consisted of high-grade stratiform "bedding-replacement" ore bodies hosted within Mississippian-aged limestones, specifically the Renault and Ste. Genevieve formations. The mine is celebrated for producing some of the finest fluorite specimens in the world, characterized by sharp cubic crystals exhibiting stunning color zoning in shades of purple, blue, yellow, and clear, often associated with sphalerite, barite, and witherite. Historically, industrial mining and quarrying at the site began in the early 1940s under the Minerva Oil Company to meet the high wartime demand for hydrofluoric acid and steel flux. The operation was a cornerstone of the regional economy for over half a century, later passing to the Ozark-Mahoning Company and eventually the Hastie Mining and Trucking Company. Large-scale commercial extraction of fluorspar in the district largely ceased by the mid-1990s due to global competition.

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