What is "brushite"

Brushite \Brush"ite\, n. [From George J. Brush, an American mineralogist.] (Min.) A white or gray crystalline mineral consisting of the acid phosphate of calcium.

n. (context mineral English) A mineral formed by the interaction of guano with calcite and clay at a low pH, believed to be a precursor of apatite.

Brushite is a phosphate mineral with the chemical formula . It forms colorless to pale yellow monoclinic prismatic crystals and as powdery or earthy masses. It is the phosphate analogue of the arsenate pharmacolite and the sulfate gypsum.