Exactly how lodestones become magnetized is a question that is up for debate. Because the Earth has a magnetic field of only 0.5 gauss, it is not strong enough to magnetize a lodestone without help. At the moment, the prevailing theory is that the strong magnetic fields which surround lightning bolts are responsible for magnetizing the lodestone. That lodestone is typically found near the surface of the Earth, instead of deep within it, helps to support that theory.
