Fluorite

specimen number:
2072358

location:
Hill-Ledford Mine, Hardin Co., Illinois, USA

description:
A cluster of purple translucent cubic fluorite crystals lustrous in measuring to 3.5 cm on edge. There are no matrix or points of attachment, slight cleaving present as seen. When backlit light shows through the edges of the piece as shown in the picture and at the end of the video.

The Hill-Ledford Mine, located in the Cave-in-Rock District of Hardin County, Illinois, is a classic example of a Mississippi Valley-Type (MVT) deposit hosted within Mississippian-aged limestone and dolomite. Geologically, the site features stratiform replacement bodies, known locally as bedded-replacement deposits, where fluorine-rich hydrothermal fluids interacted with the carbonate host rock to precipitate extensive layers of high-purity fluorite. The mine is highly regarded by mineralogists for its exceptional fluorite specimens, which frequently exhibit sharp cubic forms in various shades of yellow, purple, and blue, often found in association with sphalerite and galena. Historically, mining and quarrying in this part of the Illinois-Kentucky Fluorspar District intensified during the early to mid-20th century to meet industrial demand for steel flux and hydrofluoric acid. The Hill-Ledford operation specifically saw significant activity during the 1940s and 1950s, contributing to the region's status as the leading producer of fluorspar in the United States at that time. Although commercial mining in the district largely ceased by the mid-1990s, the Hill-Ledford Mine remains a significant historical locality for researchers studying the mineralization of the Illinois-Kentucky fluorspar belt.

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