Fluorite

specimen number:
8311419

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

description:
A grouping of near colorless translucent cubic crystals of fluorite measuring to 4.5 cm on edge are hosting a second-generation of gemmy purple cubic fluorite crystals to 1.2 cm in size. Slight cleaving present as seen, still in good condition.

The Lead Hill area, located in the Cave-In-Rock district of Hardin County, Illinois, is a historically significant locality within the Illinois-Kentucky Fluorspar District. Geologically, the site features Mississippian-aged limestone and sandstone where hydrothermal fluids deposited minerals in bedded-replacement (manto) deposits and fissure veins. Lead Hill is particularly famous for its high-quality fluorite, which often occurs as sharp, translucent to transparent cubic crystals in shades of purple, yellow, and blue, frequently associated with galena, sphalerite, and smithsonite. Historically, mining and quarrying activities in the Lead Hill vicinity began in the mid-19th century, with significant lead extraction occurring as early as 1842. The focus shifted toward industrial fluorite production in the late 1800s and early 1900s to support the growing American steel industry. While most large-scale commercial operations in the district ceased by the mid-1990s, Lead Hill remains a legendary name among mineralogists and collectors for the exceptional quality of the specimens recovered during its peak years of operation. As of 2026, the site is recognized as a classic American mineral locality, with historical records of its output preserved in major geological surveys and museum collections.

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