a mineral, probably originally uranium dioxide, UO2, but altered by radioactive decay, and usually containing uranium trioxide, lead, radium, and helium, occurring in several varieties, including pitchblende: the most important ore of uranium.
u·ra·ni·nite (yŏŏ-rā'nə-nīt') n. A complex brownish-black mineral, UO2, forming the chief ore of uranium and containing variable amounts of radium, lead, thorium, and other elements. It is isomorphous with thorianite.
[German Uranin (from New Latin ūranium, uranium; see uranium) + -ite1.]
Main Entry: ura·ni·nite Pronunciation: yu-'rA-n&-"nIt Function: noun : a mineral that is basically a black octahedral or cubic oxide ofuranium containing lead, thorium, and rare earth elements and that is the chief ore of uranium