The Collaborative International Dictionary of English v.0.48:

Loadstone \Load"stone`\, Lodestone \Lode"stone\, n. [Load, lode
   + stone.] (Min.)
   A piece of magnetite, a magnetic iron ore, possessing
   polarity like a magnetic needle, having the power to attract
   as well as to be attracted magnetically. See Magnetite.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lodestone \Lode"stone`\, n. (Min.)
   Same as Loadstone.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lodestone
    n 1: a permanent magnet consisting of magnetite that possess
         polarity and has the power to attract as well as to be
         attracted magnetically [syn: lodestone, loadstone]