Apatite

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Apatite

General
Category Mineral
Chemical formula Ca₅(PO₄)₃(F,Cl,OH)
Identification
Color Usually green, less often colorless, yellow, blue to violet.
Crystal habit Tabular, prismatic crystals, massive, compact or granular.
Crystal system Hexagonal
Cleavage Poor
Fracture Conchoidal to even
Mohs Scale hardness 5
Luster Vitreous to subresinous
Refractive index 1.632-1.646. Biref .002-.004
Pleochroism None
Streak White
Specific gravity 3.17-3.23
Major varieties
None

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH^-, F^-, or Cl^- ions, respectively, in the crystal. The formula of the admixture of the three most common species is written as Ca₅(PO₄)₃(OH, F, Cl).

Apatite

General
Category	Mineral
Chemical formula	Ca₅(PO₄)₃(F,Cl,OH)
Identification
Color	Usually green, less often colorless, yellow, blue to violet.
Crystal habit	Tabular, prismatic crystals, massive, compact or granular.
Crystal system	Hexagonal
Cleavage	Poor
Fracture	Conchoidal to even
Mohs Scale hardness	5
Luster	Vitreous to subresinous
Refractive index	1.632-1.646. Biref .002-.004
Pleochroism	None
Streak	White
Specific gravity	3.17-3.23
Major varieties
None

Apatite is one of few minerals that are produced and used by biological systems. Hydroxylapatite is the major component of tooth enamel, and a large component of bone material. Fluorapatite is slightly stronger than hydroxyapatite; thus, fluoridated water, which will allow exchange in the teeth of hydroxyl ions for fluoride ions, slightly strengthens the teeth.

Fission tracks in apatite are commonly used to determine the thermal history of orogenic (mountain) belts and of sediments in sedimentary basins.

Phosphorite is the name given to impure, massive apatite.

External links

[Apatite on Mineral galleries]

Apatite

External links

See also