What is "pharmacolite"

Pharmacolite \Phar*mac"o*lite\, n. [Gr. fa`rmakon drug, poisonous drug + -lite: cf. F. pharmacolithe.] (Min.) A hydrous arsenate of lime, usually occurring in silky fibers of a white or grayish color.

n. (context mineralogy English) A monoclinic-domatic mineral containing arsenic, calcium, hydrogen, and oxygen.

Pharmacolite is an uncommon calcium arsenate mineral with formula CaHAsO·2(HO). It occurs as soft, white clusters of fibrous crystals and encrustations which crystallize in the monoclinic system. It is the arsenate analogue of the sulfate gypsum and the phosphate brushite.