Southern Illinois was the greatest fluorspar district in the United States, and fluorite, in glassy purple, blue and yellow cubes that glow under UV, is the state mineral of Illinois. The Cave-in-Rock and Rosiclare mines around Hardin County produced it for a century, alongside fine galena, sphalerite and calcite. The mines are closed and the ground is PRIVATE, but the material is a mainstay of every rock show, and the Ben E. Clement Mineral Museum just across the river at Marion, Kentucky, holds one of the great fluorite collections.
Fluorite (Illinois state mineral)
Other places on the map within a couple of hours.
