Apatite
| 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 lattice. The formula of the admixture of the three most common species is Ca5(PO4)3(OH, F, Cl).
Apatite is one of very few minerals which 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 estimate the thermal history of sediments in sedimentary basins.
Phosphorite is the name given to impure, massive apatite.