Hydroxylapatite – Ca5(PO4)3(OH) – is the main mineral in bones, giving them their compressive strength, and, as found in nature, is often called phosphate rock. Phosphate rock is commercial mined for its phosphorus, for use in fertilizers and other purposes. Its formation is sometimes used to remove phosphorus from wastewaters, including manures. It is often also known as hydroxyapatite (that i...