Source : Webster's Revised Unabridged Dictionary (1913)

Pitchblende \Pitch"blende`\, n. [1st pitch + blende.] (Min.)
   A pitch-black mineral consisting chiefly of the oxide of
   uranium; uraninite. See {Uraninite}.

Source : WordNet®

pitchblende
     n : 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}]