Source : Webster's Revised Unabridged Dictionary (1913)

Loadstone \Load"stone`\, Lodestone \Lode"stone\, n. [Load, lode
   + stone.] (Min.)
   A piece of magnetic iron ore possessing polarity like a
   magnetic needle. See {Magnetite}.

Source : WordNet®

loadstone
     n : a permanent magnet consisting of magnetite that possess
         polarity and has the power to attract as well as to be
         attracted magnetically [syn: {lodestone}]