Fluorite; Denton Mine, near Cave-in-Rock, Illinois, USA. Photo by James St. John/Flickr (Use Permitted with Attribution).
Official State Mineral of Illinois
Fluorite was designated as the official state mineral of Illinois in 1965. All State Minerals
Illinois is the largest producer of fluorite in the United States (the most important deposits are located in southern Illinois at Rosiclare and Cave-in-Rock).
Fluorite is an important industrial mineral; it's used in the production of steel (used as a flux, or cleaning agent), to make hydrofluoric acid (for pottery, optics, and plastics), to make opalescent glass, and in enameling cookware.