Fluorite with Calcite

specimen number:
2092162

location:
Denton Mine, Hardin Co., Illinois, USA

description:
A gorgeous large crystal grouping of deep blue color zoned cubic fluorite crystals, these hosting small crystals of colorless calcite throughout. Some damage present as seen, this still really pretty. Attractive when backlit as shown in the picture and video. The colors on this can change with different lighting. Under normal indoor lighting this is a deep showy blue.

The Denton Mine, situated near Cave-in-Rock in Hardin County, Illinois, was a major producer within the world-famous Illinois-Kentucky Fluorspar District. Geologically, it is located within a complex system of faults and fractures on the northern flank of the Hicks Dome, a cryptoexplosive or alkalic igneous structure. The mineralization occurred during the Permian period when fluorine-rich hydrothermal fluids migrated upward and reacted with Mississippian-aged limestone, specifically the St. Louis and Ste. Genevieve formations, creating massive bedded replacement deposits known as mantos. Historically, the Denton Mine was developed in the late 1970s and early 1980s by the Ozark-Mahoning Company, representing one of the last large-scale underground fluorspar operations in the United States before its closure in the mid-1990s. Beyond its industrial output of acid-grade fluorspar, the mine became a legendary locality for mineral collectors due to the discovery of enormous solution cavities lined with spectacular, well-crystallized fluorite and associated sulfide minerals.

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