Fluorite (also called fluorspar) is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Crystal twinning is common and adds complexity to the observed crystal habits.
The word fluorite is derived from the Latin root fluo, meaning "to flow" because the mineral is used to increase the fluidity of slags used in smelting flux. This increase in fluidity is the result of the ionic nature of the mineral. The melting point of pure calcium fluoride is 1676 K. Fluorite gave its name to the phenomenon of fluorescence, which is prominent in fluorites from certain locations, due to certain impurities in the crystal. Fluorite also gave the name to its constitutive element fluorine.
Fluorite may occur as a vein deposit, especially with metallic minerals, where it often forms a part of the gangue (the surrounding "host-rock" in which valuable minerals occur) and may be associated with galena, sphalerite, barite, quartz, and calcite. It is a common mineral in deposits of hydrothermal origin and has been noted as a primary mineral in granites and other igneous rocks and as a common minor constituent of dolostone and limestone.
Fluorite is a widely occurring mineral which is found in large deposits in many areas. Notable deposits occur in China, Germany, Austria, Switzerland, England, Norway, Mexico, and both Ontario and Newfoundland in Canada. Large deposits also occur in Kenya in the Kerio Valley area within the Great Rift Valley. In the United States, deposits are found in Missouri, Oklahoma, Illinois, Kentucky, Colorado, New Mexico, Arizona, Ohio, New Hampshire, New York, Alaska and Texas. Fluorite has been the state mineral of Illinois since 1965. At that time, Illinois was the largest producer of fluorite in the United States; however, the last Illinois mine closed in 1995.
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