Topic summary
Hydroxylapatite
Extracted from the Wikipedia article Hydroxyapatite.
Hydroxyapatite (IMA name: hydroxylapatite) (Hap, HAp, or HA) is a naturally occurring mineral form of apatite with the formulaCa5(PO4)3(OH), often written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. It is the hydroxylendmember of the complex apatite group. The OHion can be replaced by fluoride or chloride, producing fluorapatite or chlorapatite. It crystallizes in the hexagonalcrystal system. Pure hydroxyapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis.