(redirected from Blue John)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.


(flo͞o`ərīt) or


(flo͞o`ərspär), mineral appearing in various colors, e.g., green, yellow-brown, rose, and red. Chemically, it is calcium fluoride, CaF2. Its crystals, commonly cubic, are transparent or translucent and under certain conditions exhibit fluorescence. The mineral also occurs in granular and massive forms. Fluorite is found in various parts of the world, especially in England, Germany, Mexico, and in Kentucky and Illinois in the United States. Its chief use is as a flux in metallurgy, but it is also employed in the preparation of hydrofluoric acid and in the manufacture of opal glass and enamel; some of its colorless crystals are used for making lenses and prisms.



(also fluorspar), a mineral of the fluoride group, with the chemical composition CaF2. Small amounts of Ca are sometimes replaced by Y (yielding yttrofluorite), rare-earth elements, Sr, Mn, Na, or U. Fluorite crystallizes in the isometric system, forming the fluorite structure (seeCRYSTAL STRUCTURE). Most fluorite crystals are cubes or octahedrons. The massive varieties may be composite, coarsely crystalline, granular, or earthy; one of the earthy varieties is ratovkite.

Fluorite has a hardness of 4 on Mohs’ scale, a density of 3,180–3,200 kg/m3, and a melting point of 1360°C. The density of yttrofluorite can be as high as 3,300 kg/m3. The mineral comes in various colors, for example, yellow, green, or violet. The coloration is often banded or patchy owing to the formation of color centers. Fluorite is characterized by luminescence upon exposure to ultraviolet radiation. The luminescence is caused by impurity centers: Eu2+ ions in the blue-violet region of the spectrum and Yb2+ ions in the yellow-green region. Thermoluminescence due to Mn2+ ions and triply ionized atoms of rare-earth elements is observed. Fluorite is isotropic, has a low dispersion and a low refractive index (1.434), and is transparent in the wavelength range 0.0125–10 micrometers. The transparency to such radiation makes fluorite a valuable optical raw material.

Fluorite is a common mineral and occurs in many different kinds of deposits. It is deposited overa broad temperature range, is primarily hydrothermal and metasomatic, and is sometimes found as ratovkite in sedimentary rocks. It is an important typomorphic mineral in genetic mineralogy.

Fluorite is used in metallurgy as a flux, in the chemical industry to produce hydrofluoric acid and cryolite, and in ceramics to manufacture enamels and glazes. It is also employed as the stock material for growing synthetic fluorite crystals. Pure transparent colorless or slightly tinted varieties of fluorite are used in optics to manufacture lenses, objectives, telescopes, and prisms for vacuum and X-ray spectrographs. Synthetic fluorite doped with rare-earth elements or uranium is a laser material.

The fluorite deposits in the USSR include those at Voznesenskoe in the Primor’e Krai, Solonechnoe in Middle Asia, Abagaituiskoe in Transbaikalia, and Taskainar in Kazakhstan. Outside the USSR, fluorite deposits are found in the USA, Mexico, France, and other countries. The deposits in the USA include those at Cave in Rock, 111., and in the Rocky Mountains.


Rostov, I. Mineralogiia. Moscow, 1971. (Translated from English.)
Mineraly: Spravochnik, vol. 2, issue 1. Moscow, 1963.



CaF2 A transparent to translucent, often blue or purple mineral, commonly found in crystalline cubes in veins and associated with lead, tin, and zinc ores; hardness is 4 on Mohs scale; the principal ore of fluorine. Also known as Derbyshire spar; fluor; fluorspar.


, fluor (US and Canadian), fluorite
a white or colourless mineral sometimes fluorescent and often tinted by impurities, found in veins and as deposits from hot gases. It is used in the manufacture of glass, enamel, and jewellery, and is the chief ore of fluorine. Composition: calcium fluoride. Formula: CaF2. Crystal structure: cubic
References in periodicals archive ?
The Blue John and Treak Cliff caverns in Castleton are among the Midlands' leading attractions, visited by tourists from around the world.
Mining continues today, but only on a modest scale, the mines at Blue John Cavern on Mam Tor and Treak Cliff Cavern in Buxton Road, Castleton, being more tourist attractions.
Aron continues alone and as he attempts to traverse Blue John Canyon, the rocks give way, sending him plummeting to the bottom.
One such person is Aron Ralston, an avid mountain climber who made headlines in the summer of 2003 when he became trapped in the Blue John Canyon in Utah, his arm pinned against the wall of the canyon by a heavy boulder.
One such person is Aron Ralston (James Franco), an avid mountain climber who made headlines in 2003 when his arm became trapped under a boulder in the Blue John Canyon, in Utah, and he eventually elected to amputate it with a pen knife to escape.
The film brought Ralston back to Blue John Canyon on the seventh anniversary of his entrapment.
The Oscar winner will direct 127 Hours based on mountaineer Aron Ralston's ordeal in Utah"s Blue John Canyon in 2003.
His charred body was found on a grass verge near the Blue John Mines in Castleton, Derbys, by two men out walking.
Turn to Page 62 LOUIS SAHA'S injury misfortune has cost Everton a top four spot this season, according to former Blue John Collins.
Film: Facing a crisis of conscience in canyon An amazing tale of endurance Avid mountain climber Aron Ralston (James Franco, pictured) made headlines in 2003 when he became trapped in the Blue John Canyon in Utah, his arm pinned by a heavy boulder.
THE TELEGRAPH 127 HOURS (15) ARON Ralston (James Franco) is an avid mountain climber who made headlines in the summer of 2003 when he became trapped in the Blue John Canyon in Utah, his arm pinned against the wall of the canyon by a heavy boulder.