The Collaborative International Dictionary of English v.0.48:

Uraninite \U*ran"i*nite\, n. (Min.)
   A mineral consisting chiefly of uranium oxide with some lead,
   thorium, etc., occurring in black octahedrons, also in masses
   with a pitchlike luster; pitchblende.
   [1913 Webster]

WordNet (r) 3.0 (2006):

uraninite
    n 1: 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 [syn: uraninite, pitchblende]