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Pure fluorite is colourless and transparent, both in visible and ultraviolet light, but impurities usually make it a colorful mineral 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 main uses of fluoride, in terms of volume, are in the production of cryolite, Na 3 AlF 6. It is used in aluminium smelting. Formerly, it was mined, but now it is derived from hydrogen fluoride. Fluorite is used on a large scale to separate slag in steel-making. Mined fluorite (CaF 2) is a commodity chemical used in steel-making.
Its use began in the 1940s, following studies of children in a region where water is naturally fluoridated. It is now used widely in public water systems in the United States and some other parts of the world, such that about two-thirds of the U.S. population is exposed to fluoridated water supplies [5] and about 5.7% of people worldwide. [6]
Fluorite of the acidspar grade is used directly as an additive to ceramics and enamels, glass fibers and clouded glass, and cement, as well as in the outer coating of welding rods. [5] Acidspar is primarily used for making hydrofluoric acid, which is a chemical intermediate for most fluorine-containing compounds.
Fluorapatite (Ca 5 (PO 4) 3 F) is mined along with other apatites for its phosphate content and is used mostly for production of fertilizers. Most of the Earth's fluorine is bound in this mineral, but because the percentage within the mineral is low (3.5%), the fluorine is discarded as waste. Only in the United States is there significant recovery.
Fluorite, the primary mineral source of fluorine, which gave the element its name, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the Latin verb fluo meaning ' to flow ' gave the mineral its name. Proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its ...
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In alkaline-to-neutral aqueous solutions, hexafluorosilicic acid readily hydrolyzes to fluoride anions and amorphous, hydrated silica ("SiO 2 "). Strong bases give fluorosilicate salts at first, but any stoichiometric excess begins hydrolysis. [7] At the concentrations usually used for water fluoridation, 99% hydrolysis occurs: [6] [8] SiF 2−