Fluorite was designated as the official state mineral of Illinois in 1965. 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).
Mazon Creek is an important Pennsylvanian age deposit with a great diversity of fossil organisms with a remarkable quality of preservation, many times both hard and soft parts are preserved. Most fossils are found in concretions (siderite nodules) along the Mazon River area of the Illinois. One public collecting area is now a state park managed by the Illinois Department of Natural Resources.
A day permit is required to collect fossils and may be obtained from the park office or Web site. A reporting form also is available for reporting what was found. Excavations and collecting for commercial purposes are prohibited. Fossil collecting is restricted from March 1 to September 30.