Fluorite Cleavage Octahedron from the Hill-Ledford Mine, Cave-In-Rock, Illinois
Contributed by: Chris Clemens
minID: FJ9-3UX
Date: Apr 17th, 2026
Locality: Hill-Ledford Mine, Cave-In-Rock Mining Sub-District, Hardin County, Illinois, USA (See on Mindat)
Size: 5.4 x 5.4 x 5.4 cm
Weight: 202 g
Description:
This is a large, transparent, purple fluorite cleavage octahedron from the Hill-Ledford mine, in Cave-In-Rock, Hardin County, Illinois. Under UV, this specimen shows a deep, saturated blue, fluorescent response.
The Hill-Ledford Mine was one of the many notable fluorspar mines in the Illinois/Kentucky fluorspar district, and was operated by the Ozark-Mahoning Company from the late 1950's into the 1970's.
Fluorescence under long wave UV (365 nm) produces an intense, saturated, deep blue color. Although not evident in the LW photograph, the brightest response is seen under longwave UV, but it is difficult to accurately depict due to limitations of the camera's image sensor. The blue fluorescence under UV is activated by the well-known mechanism of divalent europium substituting for some of the calcium ions in the fluorite crystal structure.
Originally posted by Chris Clemens on Nature's Rainbows in 2021.
Summary of luminescence responses:
Fluorite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Blue
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue