The phosphate ion, (PO43−), is the conjugate base of phosphoric acid. It has many different salts and mineral forms. Phosphate rock is a general term referring to rock with high concentrations of phosphate minerals. Historically, the most common sources of phosphate rock are guano, (the accumulate excrement of seabirds and bats) and apatite minerals (Ca5(F,Cl,OH)(PO4)3). Phosphate rocks are concentrated via froth flotation and typically produce a concentrate with 50% equivalent phosphorus pentoxide (P2O5).
Beneficiated phosphate rock can be solubilized to produce phosphoric acid or smelted to produce elemental phosphorus. The majority of mined phosphate rock is used to produce fertilizer via the reaction with phosphoric acid to produce superphosphate or with anhydrous ammonia to produce ammonium phosphate fertilizers.