Fluorite with Calcite

specimen number:
2102185

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

description:
A cluster of glassy mostly gemmy beautiful blue cubic fluorite crystals, the largest measuring to 1.8 cm on edge, with little attached matrix and associated crystals of calcite. In good condition with very minimal micro-damage present. Beautiful when backlit as shown at the end of the video.

The Minerva No. 1 Mine, located near Cave-in-Rock in Hardin County, Illinois, was one of the most productive and mineralogically significant operations in the Illinois-Kentucky Fluorspar District. Geologically, it was a bedded-replacement deposit hosted within the Mississippian-aged Mississippian-aged St. Louis and Ste. Genevieve Limestones, where fluorine-bearing hydrothermal fluids replaced favorable limestone layers under a cap of impermeable shale. The mine is legendary for its spectacular mineral specimens, specifically multi-colored cubic fluorite often exhibiting complex zoning in shades of yellow, purple, and blue, frequently accompanied by sharp crystals of witherite, barite, and sphalerite. Historically, the mine began operations in 1942 under the Minerva Oil Company and served as a vital source of fluorspar for the steel and chemical industries for decades. It later became part of the Ozark-Mahoning Company holdings and remained a major producer until the general decline of the district led to its permanent closure in 1996. Even decades after its decommissioning, the Minerva No. 1 remains a hallmark locality for collectors due to the exceptional aesthetic quality and variety of its mineral combinations.

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