from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A mineral formed by the interaction of guano with calcite and clay at a low pH, believed to be a precursor of apatite.
from the GNU version of the Collaborative International Dictionary of English
- n. A white or gray crystalline mineral consisting of the acid phosphate of calcium.
from The Century Dictionary and Cyclopedia
- n. A hydrated phosphate of calcium found in the guano of Aves Islands and Sombrero in the West Indies, in slender monoclinic crystals of a pale-yellow color.
Arsenate is removed by being exchanged for phosphate in the mineral brushite, a crystalline structure found in the stones.
The mineral brushite, CaHPO_4·2H_2O, which is isomorphous with the acid arsenate pharmacolite, CaHAsO_4·2H_2O, is an acid phosphate, and assumes monoclinic forms.