Brushite

Brushite is a mineral, formula CaHPO4·2H2O. It is believed to be precursor of apatite and is found in guano-rich caves; formed by the interaction of guano with calcite and clay at a low pH.

The other source of brushite is from calcium phosphate kidney stones, the original precipitating material is usually brushite. 9% of supragingival calculus consist of brushite

Brushite Brushiet