Fluorite

Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon.Pastel green fluorite crystal on galenaA golden yellow with hints of purple fluoriteFreestanding purple fluorite cluster between two quartzesLight to dark burgundy color fluoriteTransparent teal color fluorite with purple highlightsGrass-green fluorite octahedrons clustered on a quartz-rich matrixFluorite crystals on display at the Cullen Hall of Gems and Minerals, Houston Museum of Natural ScienceFluorite and sphalerite, from Elmwood mine, Smith county, Tennessee, USTranslucent ball of botryoidal fluorite perched on a calcite crystalFluorite with baryte, from Berbes Mine, Berbes Mining area, Ribadesella, Asturias, SpainFluorite and galena from Rogerley Mine, Weardale, North Pennines, England, UKFluorite from El Hammam Mine, Meknès Prefecture, Meknès-Tafilalet Region, Morocco Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 4 as Fluorite. Fluorite is a colorful mineral, both in visible and ultraviolet light, and the stone has ornamental and lapidary uses. Industrially, fluorite is used as a flux for smelting, and in the production of certain glasses and enamels. The purest grades of fluorite are a source of fluoride for hydrofluoric acid manufacture, which is the intermediate source of most fluorine-containing fine chemicals. Optically clear transparent fluorite lenses have low dispersion, so lenses made from it exhibit less chromatic aberration, making them valuable in microscopes and telescopes. Fluorite optics are also usable in the far-ultraviolet and mid-infrared ranges, where conventional glasses are too absorbent for use. The word fluorite is derived from the Latin verb fluere, meaning to flow. The mineral is used as a flux in iron smelting to decrease the viscosity of slags. The term flux comes from the Latin adjective fluxus, meaning flowing, loose, slack. The mineral fluorite was originally termed fluorospar and was first discussed in print in a 1530 work Bermannvs sive de re metallica dialogus , by Georgius Agricola, as a mineral noted for its usefulness as a flux. Agricola, a German scientist with expertise in philology, mining, and metallurgy, named fluorspar as a neo-Latinization of the German Flussspat from Fluß (stream, river) and Spat (meaning a nonmetallic mineral akin to gypsum, spærstān, spear stone, referring to its crystalline projections). In 1852, 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. Presently, the word 'fluorspar' is most commonly used for fluorite as the industrial and chemical commodity, while 'fluorite' is used mineralogically and in most other senses. In the context of archeology, gemmology, classical studies, and egyptology, the Latin terms murrina and myrrhina refer to fluorite. In book 37 of his Naturalis Historia, Pliny the Elder describes it as a precious stone with purple and white mottling, whose objects carved from it, the Romans prize. Fluorite crystallises in a cubic motif. Crystal twinning is common and adds complexity to the observed crystal habits. Fluorite has four perfect cleavage planes that help produce octahedral fragments. Element substitution for the calcium cation often includes certain rare earth elements (REE), such as yttrium and cerium. Iron, sodium, and barium are also common impurities. Some fluorine may be replaced by the chloride anion. Fluorite is a widely occurring mineral that occurs globally with significant deposits in over 9,000 areas. It 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 dolomite and limestone.