uraninite
nounA 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.
nounA mineral of a pitch-black color and very heavy, having when unaltered a specific gravity of 9.5.
nounThis mineral, in its different varieties (the crystallized kinds called cleveite, bröggerite, nivenite, etc., and the more abundant amorphous and impure pitchblende), has become of much importance as being the chief source of radium. See
A mineral consisting chiefly of uranium oxide with some lead, thorium, etc., occurring in black octahedrons, also in masses with a pitchlike luster; pitchblende.
nounAny of several brownish-black forms of uranium dioxide,
a mineral consisting of uranium oxide and trace amounts of radium and thorium and polonium and lead and helium; uraninite in massive form is called pitchblende which is the chief uranium ore