Fluorite

specimen number:
8311490

location:
Lead Hill, Hardin Co., Illinois, USA

description:
Light purple cubic crystals of fluorite over the top of a previous generation of larger colorless cubic fluorite crystals. Minor chalcopyrite present. In good condition with very minimal cleaving present.

The Lead Hill area, located within the historic Illinois-Kentucky Fluorspar District in Hardin County, Illinois, is situated over a series of Mississippian-aged limestone and sandstone units. Geologically, the deposit consists of structural vein and bedded-replacement mineralization formed by hydrothermal fluids migrating along the Cincinnati Arch and associated fault systems. The locality is famous for producing high-quality fluorite, which occurs in a variety of colors including yellow, purple, and blue, often forming sharp cubic crystals that may be associated with galena or sphalerite. Historically, mining and quarrying at Lead Hill began as early as the 1840s, primarily targeting lead ore, but shifted toward fluorite production as its industrial value as a flux in steelmaking increased during the late 19th and early 20th centuries. Operations in this specific area were most active through the mid-1900s, contributing to the district's status as a top global producer before large-scale mining in the region ceased in the late 1990s. As of 2026, Lead Hill remains a classic American locality, frequently cited in mineralogical records for its historical significance and its contribution to the storied heritage of Illinois fluorite.

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