Fluorite with Calcite

specimen number:
2242040

location:
Ozark-Mahoning #1 Mine, Hardin Co., Illinois, USA

description:
Very attractive blue with yellow interior cubic crystal grouping of fluorite, this hosting colorless crystals of calcite. In very good condition. The specimen is quite attractive when backlit as shown in the picture and at the end of the video.

The Ozark-Mahoning Mine No. 1, also known simply as the Mahoning No. 1, was located in the Cave-in-Rock District of Hardin County, Illinois, and served as a foundational operation for the region's fluorspar industry. Geologically, the mine exploited rich bedding-replacement deposits within the Mississippian-aged Fredonia Limestone and the Rosiclare Sandstone member, where fluorine-rich hydrothermal fluids reacted with the carbonate host rock. The site is famous for its exceptional fluorite specimens, which typically feature large, well-formed cubic crystals in colors ranging from deep purple and lavender to honey-yellow, often accompanied by sphalerite, galena, and frosted barite. Historically, mining and quarrying activities at the No. 1 began in the late 1930s following the merger of the Mahoning Mining Company and the Ozark Chemical Company. This mine was a critical producer of acid-grade fluorspar during World War II and continued to operate as a primary hub for the Ozark-Mahoning Company through the 1950s and 1960s. Although underground operations eventually shifted to newer shafts like the Annabel Lee and Denton as the No. 1 reserves were exhausted, it remains a cornerstone locality for understanding the mineralization of the Illinois-Kentucky Fluorspar District.

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