Source : Webster's Revised Unabridged Dictionary (1913)

Magnetite \Mag"net*ite\, n. (Min.)
   An oxide of iron ({Fe3O4}) occurring in isometric crystals,
   also massive, of a black color and metallic luster. It is
   readily attracted by a magnet and sometimes possesses
   polarity, being then called {loadstone}. It is an important
   iron ore. Called also {magnetic iron}.

Source : WordNet®

magnetite
     n : an oxide of iron that is strongly attracted by magnets [syn:
          {magnetic iron-ore}]