| Fluorapatite | |
|---|---|
 Fluorapatite (pink) on top of muscovite (green) | |
| General | |
| Category | Phosphate mineral Apatite group |
| Formula (repeating unit) | Ca5(PO4)3F |
| IMA symbol | Fap[1] |
| Strunz classification | 8.BN.05 |
| Crystal system | Hexagonal |
| Crystal class | Dipyramidal (6/m) H-M symbol: (6/m) |
| Space group | P63/m |
| Identification | |
| Color | Sea-green, violet, purple, blue, pink, yellow, brown, white, colorless, may be zoned |
| Crystal habit | Massive to prismatic crystalline |
| Twinning | Contact twins rare |
| Cleavage | Indistinct |
| Fracture | Brittle to conchoidal |
| Mohs scale hardness | 5 |
| Luster | Vitreous, resinous to dull |
| Streak | White |
| Diaphaneity | Transparent to opaque |
| Specific gravity | 3.1 to 3.2 |
| Optical properties | Uniaxial (−) |
| Refractive index | nω = 1.631 – 1.650 nε = 1.633 – 1.646 |
| Birefringence | δ = 0.002 |
| Ultraviolet fluorescence | Fluorescent and phosphorescent |
| References | [2][3][4] |
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, yellow, violet, or colorless), the pure mineral is colorless, as expected for a material lacking transition metals. Along with hydroxylapatite, it can be a component of tooth enamel, especially in individuals who use fluoridated toothpaste, but for industrial use both minerals are mined in the form of phosphate rock, whose usual mineral composition is primarily fluorapatite but often with significant amounts of the other.[5]
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.[5] 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.[2]
Fluorapatite is found in the teeth of sharks and other fishes in varying concentrations. It is also present in human teeth that have been exposed to fluoride ions, for example, through water fluoridation or by using fluoride-containing toothpaste. The presence of fluorapatite helps prevent tooth decay or dental caries.[6] Fluoroapatite has a mild bacteriostatic property as well, which helps decrease the proliferation of Streptococcus mutans, the predominant bacterium related to dental caries.[7]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ a b "Fluorapatite" Archived 2012-02-08 at the Wayback Machine. Handbook of Mineralogy.
- ^ Apatite-(CaF) Mineral Data Archived 2016-10-30 at the Wayback Machine. webmineral.com.
- ^ "Fluorapatite". mindat.org. Archived from the original on 2018-03-08. Retrieved 2013-11-17.
- ^ a b Klein, Cornelis; Hurlbut, Cornelius Searle; Dana, James Dwight (1999), Manual of Mineralogy (21 ed.), Wiley, ISBN 0-471-31266-5
- ^ "How does fluoride protect my teeth and make them strong?". UCSB Science Line. Regents of the University of California. Archived from the original on 27 October 2017. Retrieved 3 June 2016.
- ^ Trushkowsky, Richard. "The science of caries diagnosis" Archived 2016-07-01 at the Wayback Machine. Dentistry IQ.