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Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blue, violet, or colorless), the pure mineral is colorless as expected for a material lacking transition metals. Along with hydroxylapatite, it is an important constituent of tooth enamel.〔 〕 Fluorapatite crystallizes in a hexagonal crystal system. It is often combined as a solid solution with hydroxylapatite (Ca5(PO4)3OH or Ca10(PO4)6(OH)2) in biological matrices. Chlorapatite (Ca5(PO4)3Cl) is another related structure.〔 Industrially, the mineral is an important source of both phosphoric and hydrofluoric acids. Fluorapatite as a mineral is the most common phosphate mineral. It occurs widely as an accessory mineral in igneous rocks and in calcium rich metamorphic rocks. It commonly occurs as a detrital or diagenic mineral in sedimentary rocks and is an essential component of phosphorite ore deposits. It occurs as a residual mineral in lateritic soils.〔 Fluorapatite is also found in teeth. It is found in the shark tooth. Fluoride is also found in the teeth of other fishes in varying concentration. And fluorapatite is also found in human teeth that have been exposed to fluoride ions, for example, through water fluoridation or by using fluoride toothpaste. The presence of fluorapatite helps prevent decay, as it does not dissolve in the acids produced by ''Streptococcus mutans'' bacteria in the mouth. Typically, dental hydroxylapatite far exceeds the fluorapatite produced during periods of exposure to fluoride. ==Synthesis== Fluorapatite can be synthesized in a two step process. First, calcium phosphate is generated by combining calcium and phosphate salts at neutral pH.This material then reacts further with fluoride sources (often sodium monofluorophosphate or calcium fluoride (CaF2)) to give the mineral. This reaction is integral in the global phosphorus cycle.〔Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.〕 :3 + 2 → :3 + → 2 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fluorapatite」の詳細全文を読む スポンサード リンク
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