fluorite n : a soft mineral (calcium fluoride) that is fluorescent in ultraviolet light; chief source of fluorine [syn: fluorspar, fluor]

English

Noun

fluorite

1. a widely occuring mineral, (calcium fluoride), of various colours, used as a flux in steelmaking, and in the manufacture of glass, enamels and hydrofluoric acid

Translations

• Estonian: fluoriit
• Italian: fluorite
• Japanese: 蛍石 (ほたるいし, hotaruishi)

Synonyms

• calcium fluoride
• Derbyshire spar
• fluor
• fluorspar

See also

• blue john

Italian

Noun

fluorite

1. fluorite

Fluorite (also called fluorspar) is a 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. Cubic crystals up to 20 cm across have been found at Dalnegorsk, Russia. 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 has a relatively low melting point and was used as an important flux in smelting. Fluorite gave its name to its constitutive element fluorine.

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 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 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. 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 fluoresce under ultra-violet light, a property that takes its name from fluorite. Many minerals, as well as other substances, fluoresce. Fluorescence involves the elevation of electron energy levels by quanta of ultra-violet light, followed by the progressive falling back of the electrons into their previous energy state, releasing quanta of visible light in the process. In fluorite, the visible light emitted is most commonly blue, but red, purple, yellow, green and white also occur. The fluorescence of fluorite may be due to impurities such as yttrium or organic matter in the crystal lattice. It is not surprising, therefore, that the color of visible light emitted when a sample of fluorite is fluorescing appears dependent on where the original specimen was collected, different impurities having been included in the crystal lattice in different places. Neither do all fluorites fluoresce equally brightly, even from the same locality. Therefore 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

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

External links

• an educational tour of Weardale Fluorite
• Illinois State Geologic Survey
• Illinois state mineral
• Barber Cup and Crawford Cup, related Roman cups at British Museum.
• Fluorites and antifluorites at NCSU
• Spanish Fluorite