Fluorite

Fluorite (also called fluorspar) is a crystal habits.

The name fluorite is derived from the Latin fluo, meaning "flow", in reference to its industrial use as a flux.

Occurrence

Fluorite may occur as a vein deposit, especially with metallic minerals, where it often forms a part of the gangue (the worthless "host-rock" in which valuable minerals occur) and may be associated with limestone.

Fluorite is a widely occurring mineral which is found in large deposits in many areas. Notable deposits occur in Germany, Austria, Switzerland, England, Norway, Mexico, and Ontario 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. Illinois has historically been the largest producer of fluorite in the United States, however, the last of the mines closed in 1995.[1] The Illinois general assembly passed a resolution in 1965 declaring fluorite as the official state mineral.

Blue John

  One of the most famous of the older-known localities of fluorite is Castleton in Derbyshire, England, where, under the name of Derbyshire Blue John, purple-blue fluorite was extracted from several mines/caves, including the famous Blue John Cavern. During the 19th century, this attractive fluorite was mined for its ornamental value. The name derives from French "bleu et jaune" (blue and yellow) characterising its color. Blue John is now scarce, and only a few hundred kilograms are mined each year for ornamental and lapidary use. Mining still takes place in the nearby Treak Cliff Cavern. Recent deposits in China have produced fluorite with coloring and banding similar to the classic Blue John stone.

Fluorescence

  Many samples of fluorite ultra-violet light is not a reliable tool for the identification of specimens, nor for quantifying the mineral in mixtures. For example, among British fluorites, those from Northumberland, County Durham and Eastern Cumbria are the most consistently fluorescent, whereas fluorites from Yorkshire, Derbyshire and Cornwall, if they fluoresce at all, are generally only feebly fluorescent.

Fluorite also exhibits the property of thermoluminescence.

Uses

  There are three principal types of industrial use for fluorite, corresponding to different grades of purity. Metallurgical grade fluorite, the lowest of the three grades, has traditionally been used as a perfluorocarbons, and is also used to etch glass.

Fluorite is used instead of glass in some high performance telescopes and camera lens elements. Exposure tools for the ultraviolet light at 157 nm wavelength. Fluorite has a uniquely high transparency at this wavelength. Fluorite has a very low dispersion so lenses made from it exhibit less chromatic aberration than those made of ordinary glass. In telescopes it allows crisp images of astronomical objects even at high power. Fluorite also has ornamental and lapidary uses.

See also

• List of minerals

References

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, pp. 324 - 325, 20th ed., ISBN 0-471-80580-7
• Mineral Galleries
• Webmineral
• Mindat.org
• Fluorspar

1. ^ The Complete Encyclopedia of Minerals by P. Korbel and M. Novak

Gallery