Cave-in-Rock Hardin County Fluorite

Cave-in-Rock Hardin County, Illinois has a long history of producing some of the worlds finest fluorite specimens. There were many mines in the Southern Illinois/Northern Kentucky area but 3 mines became very famous to Rockhounds due to the many forms of fluorite found there. The three best known mines are the Minerva Mine which was sunk in 1942 and is 680 feet deep. The Denton Mine is 640 feet deep and was put into operation in 1981 while the Anna Belle Lee Mine was brought on line in 1984 at a depth of nearly 1,000 feet. Due to the tilt or dip of the rock units, some places in the mines are 1200 to 1300 feet below the surface. These mines have been closed for some time now. Although we hear that there is a mining company boring a new mine, we have seen no fluorite from that location as of yet.

Fluorite is a widespread and common mineral. It often occurs as a primary mineral in veins or as a mix of lead, zinc and silver ores. Fluorite is also found in sedimentary rocks such as limestones and dolomites as well as in igneous rocks such as granites. Fluorite occurs commonly as cubic, octahedral and dodecahedral crystals in many different colors ranging from colorless and completely transparent to yellow, green, blue, purple, pink or black. Crystals may be large and penetration twins are fairly common. “Hoppered” specimens are in great demand. Fluorite may glow blue or violet in SW or MW ultraviolet light.