2" Chalcopyrite Crystals on Purple-Yellow Fluorite - Cave-in-Rock

The Cave-In-Rock mining district of Hardin County, Illinois is world renowned for its fluorite, which is widely considered to be some of the highest quality fluorite in the world. The area has a long history of producing spectacular fluorite specimens from several different mines. All of the major mines have been closed for years and the cutoff in supply has sent prices of this material soaring. A recently bored mine is now producing small amounts of material, but hasn't made a dent in demand or prices.

Archaeological discoveries near the Cave-In-Rock mining district found beads and other ornaments made of fluorite, placing use of the stone in the area to about 900 years ago, when the land was inhabited by the Native Mississippian Americans. Early European settlers mining for galena in the 1830s discarded fluorite they mined, since the lead they sought was more valuable at the time. Fluorite found new use in the 1880s in a new steel-furnace technology and demand increased considerably, leading to the emergence of several commercial fluorite mining companies in the Illinois/Kentucky region.

Fluorite is a halide mineral comprised of calcium and fluorine with the chemicla formula CaF2. The word "fluorite" is from the Latin fluo, which means to flow. In 1852 fluorite gave its name to the phenomenon known as fluorescence, or the property of fluorite to glow a different color depending upon the bandwidth of the ultraviolet light it is exposed to.

Fluorite occurs commonly in cubic, octahedral and dodecahedral crystals in many different colors. These colors range from colorless and completely transparent to yellow, green, blue, purple, pink or black. It is most commonly found in purple and/or green.