Lodestone is a naturally occurring magnet made of magnetite, which is an oxide of iron. Unlike ordinary rust, magnetite forms when iron oxidizes under very dry conditions. Lodestone is the strongest magnet found in nature.
The earliest reference to lodestone in literature is by Thales of Miletus, a Greek philosopher from the sixth century B.C., who believed the attraction of iron to lodestone is due to the mineral possessing a soul. While his contemporaries developed other theories, lodestone remained a mystery to most. With little knowledge of how lodestone worked, the Chinese developed crude compasses using its magnetic properties.
Magnetite must have the required composition and crystalline structure to develop the properties of a lodestone. Research has shown that lightning strikes bring the energy needed to orient the structure so that the natural stone develops a magnetic charge. In laboratories, scientists create artificial lightning strikes to simulate the magnetization of magnetite.
All iron materials have magnetic domains. In those that do not show magnetic properties, the domains are oriented in many different directions. However, in lodestone and other magnetic materials, the domains are all oriented in the same direction, giving the magnet a north pole and south pole. When the oriented material, whether natural or synthetic, is broken, it forms two smaller magnets, both with poles identical to the original magnet that was broken.