Apatite is a phosphate-bearing mineral with the chemical formula Ca5[PO4]3. It has a hexagonal crystal system, and the crystals are hexagonal columns. The aggregates are granular, dense block or nodule-like. Apatite has several colours, such as grey, brownish yellow and light green. It has a vitreous lustre, and the fractures are uneven and greasy. Its specific gravity is 3.2, and its Mohs hardness is 5. It can form from endogenous, exogenous and metamorphic processes. It is an important raw material for the manufacturing of agricultural phosphate fertilizer and for phosphorus extraction. Hydroxyapatite crystals can be used as laser-emitting materials.