Illinois State Mineral – Flourite

Pure fluorite (CaF2) is made of the elements calcium (Ca) and fluorine (F)

Fluorite - Photo by SDCDeaCerte/Flickr

Fluorite melts at low temperatures and flows through other minerals, such as limestone, which is where it gets its name. Fluere in Latin, means to flow. Minerals formed like this are called hydrothermal deposits. In it’s purest form, fluorite is clear, shiny, and transparent, but because it flows through other minerals as it’s forming, it picks up trace minerals and turns into myriad colors.

The United States used to be a major producer of fluorite. Fluorite was mined in southeastern Illinois from the early 1800s. Originally, Kentucky was the leading producer, but from the 1940s to the 1990s Illinois led the way in fluorite production, producing up to 50% of all U.S. fluorspar ore. Most of the mining was done underground, as far down as 1300 feet, but there were a few open pit mines in the region. Cheaper imports began to displace the U.S. production of fluorspar, and according to the Illinois Department of Natural Resources, the last mine in Illinois, and the U.S., closed for good in December 1995.

The many uses for fluorite

Native Americans carved fluorspar to make artifacts, but the first recorded use of Illinois’ fluorite was in 1823, when fluorspar mined near Shawneetown in Gallatin County was used to manufacture hydrofluoric acid. The mineral fluorite is vital to the nation’s economy. Its uses:

Mineral
smelting iron, aluminum, and other metal alloys

• manufacturing glass, enamel glazes, ceramics, portland cement, and many chemical compounds

Hydrofluoric acid

• refining aluminum
• refining uranium fuel for nuclear reactors
• making rocket fuel and metal plating

Inorganic fluoride chemicals

• toothpastes
• special fluxes for welding rods
• optical lenses and concrete hardeners

Organic fluoride chemicals

• Plastics, refrigerants, nonstick coatings,
  lubricants, stain repellents, dyes, herbicides, medicines and anesthetics, cleaning solvents, degreasing agents and foaming agents.
• One of the most widely used organic fluoride compounds, the refrigerant Freon(tm), is no longer produced in the United States. The chlorine in the compound is thought to damage the protective ozone layer that shields the earth from ultraviolet radiation.

D.L. Reinertsen and J.M. Masters, Fluorite: The Illinois State Mineral, Illinois Department of Natural Resources.