pharmacolite

from The Collaborative International Dictionary of English v.0.48

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.
   [1913 Webster]