Fluorite

specimen number:
2242018

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

description:
Glassy gemmy color zoned crystals of fluorite to 4.0 cm on edge across the top of a yellowish naturally etched crystallized fluorite matrix. Very slight micro-damage present not atypical of these, this is in good condition. Beautiful when backlit as shown in the picture and video. There are inclusions of hydrocarbon present.

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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