This image shows SEM photo of crystal structures of HA coating on Ti4Al6V alloy synthesised by electrochemical deposition method where crystals are morphologica — Photo: Nabilah · CC BY-SA 4.0
Hydroxylapatite
Also known as: Hydroxyapatite, Bone mineral.
The hydroxyl member of the apatite group — calcium phosphate that is the principal mineral of bones and teeth.
Intro adapted from Wikipedia (CC BY-SA).
Hydroxylapatite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₅(PO₄)₃OH.
It crystallizes in the hexagonal crystal system (space group P6_3/m). It is a member of the Apatite structural group.
Key properties: Mohs hardness 5; specific gravity 3.14–3.21; typically white or colorless or gray; white streak; Vitreous to subresinous, earthy luster; refractive index 1.648; optically uniaxial.
IMA symbol Hap, IMA status: approved, named in 1856.
Much less common than fluorapatite. Formed by the reaction of limestone with phosphatic solutions derived from guano. In talc schists in association with serpentinite.
It is found associated with Brushite, calcite (caves); talc, serpentine (schists); montebrasite, crandallite, muscovite (pegmatite).
The name refers to dominant hydroxyl and membership in the apatite group; see fluorapatite.
Collections: Everyday Minerals.