Fluorite (cleavage Octahedron)

specimen number:
2092245

location:
Southern Illinois Fluorspar District, Illinois, USA

description:

Attractive golden yellow cleavage fluorite octahedron. The size provided is measured from point to point. Attractive when backlit as seen in the picture and at the end of the video.

The Southern Illinois Fluorspar district, centered around the historic communities of Rosiclare and Cave-in-Rock in Hardin County, Illinois, is the most celebrated fluorite-producing region in the United States, famous for producing generations of miners who mastered the craft of geometric hand-cleaving to produce sharp, flawless cleavage octahedrons. Geologically, these world-class deposits occur as extensive, low-temperature, Mississippi Valley-type (MVT) hydrothermal vein and bedded replacement deposits hosted within Mississippian-age sedimentary limestones, sandstones, and shales. The massive, high-purity fluorite crystallized in vast, colorful layers of yellow, blue, and deep purple, possessing a perfect octahedral cleavage on the (111) crystal planes that allowed miners and collectors to deftly tap the material along its natural weaknesses to reveal beautiful, multi-colored geometric diamonds. Historically, commercial mining and quarrying for fluorspar in the district began on a small scale around 1842, expanding into a massive strategic industry during the 20th century to supply critical metallurgy flux for the steel and chemical industries. Large-scale corporate underground operations operated systematically through decades of peak production before low-cost foreign competition and declining domestic reserves forced the final major mines, including the famous Ozark-Mahoning mining complex, to permanently cease extraction in 1995. Through 2026, original hand-cleaved fluorite octahedrons from this iconic Illinois district remain highly prized, nostalgic collector benchmarks representing a uniquely American mineral folk art and regional mining heritage.

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