Hydroxyapatite, abbreviated as HAP, has powder, porous particles and massive form. It consists of two parts, hydroxyl apatite. It can form chemical bond with the body tissue, has certain solubility, and can release harmless ions to participate in metabolism. 
Melting point: 1650 ° C 
Solubility: 0.4 ppm 
is usually produced by a precipitation method, hydrolysis method, hydrothermal method, solid phase method, or the like.