Fluorite

specimen number:
2092263

location:
Annabel Lee Mine, Hardin Co., Illinois, USA

description:
Attractive cluster of translucent purple cubic fluorite crystals. In good condition with minimal cleaving present. Beautiful when backlit as seen in the picture and at the end of the video.

The Annabel Lee mine, situated in Hardin County within the historic Illinois-Kentucky Fluorspar District, was one of the last major underground operations developed to extract high-grade fluorite in the United States. Geologically, the deposit is a classic example of a bedding-replacement (manto) system hosted within Mississippian-age sedimentary rocks, specifically the St. Louis and Ste. Genevieve Limestones. Hydrothermal fluids migrating along regional faults dissolved the limestone beds and precipitated thick, stratified layers of fluorite, creating open cavities where mineralized solutions grew cubic crystals of fluorite, typically showing distinct color zoning in shades of purple, yellow, and blue, intimately associated with sphalerite, galena, barite, and calcite. Historically, underground shaft sinking and development at the Annabel Lee property began in 1891 under the Ozark-Mahoning Company, with formal commercial production commencing in 1894. The mine operated as a modern, highly efficient industrial facility, producing substantial quantities of metallurgical and acid-grade fluorspar to support domestic steel and chemical manufacturing, until severe economic competition from cheaper foreign imports and declining domestic reserves forced a permanent cessation of all mining operations at the site in 1995, marking the end of an era for the entire mining district.

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