Meaning of crookesite

crookes•ite

Pronunciation: (krook'sīt), [key]
— n.
  1. a rare mineral, selenide of copper, thallium, and silver, (Cu, Tl, Ag)Se, occurring in steel-gray, compact masses.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.