A massive variety of apatite.
sedimentary rock composed largely of calcium phosphate, usually as a variety of the mineral apatite and largely in the form of concretions and nodules. Primary ore of phosphate minerals and elemental phosphorus.
a sedimentary rock composed chiefly of phosphate minerals
Rock containing quantities of precipitated or reworked phosphate minerals.
a rock consisting chiefly of calcium phosphate. It is a primary source of phosphorus for agriculture. [AHDOS