Fluorapatite

Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca₅(PO₄)₃F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blue, violet, or colorless), the pure mineral is colorless as expected for a material lacking transition metals. Along with hydroxylapatite, it is an important constituent of tooth enamel.

Fluorapatite crystallizes in a hexagonal crystal system. It is often combined as a solid solution with hydroxylapatite (Ca₅(PO₄)₃OH or Ca₁₀(PO₄)₆(OH)₂) in biological matrices. Chlorapatite (Ca₅(PO₄)₃Cl) is another related structure. Industrially, the mineral is an important source of both phosphoric and hydrofluoric acids.

Fluorapatite as a mineral is the most common phosphate mineral. It occurs widely as an accessory mineral in igneous rocks and in calcium rich metamorphic rocks. It commonly occurs as a detrital or diagenic mineral in sedimentary rocks and is an essential component of phosphorite ore deposits. It occurs as a residual mineral in lateritic soils.