Lodestone - Definition and Overview

Magnetite

Lodestone or loadstone refers to either:

• Magnetite, a magnetic mineral form of iron(II), iron(III) oxide Fe₃O₄, one of several iron oxides.

• A piece of intensely magnetic magnetite that was used as an early form of magnetic compass.

Iron, steel and ordinary magnetite are attracted to a magnetic field, including the Earth's magnetic field. Only magnetite with a particular crystalline structure, lodestone, can act as a natural magnet and attract and magnetize iron. The ability to use a lodestone as a compass is thought to have been discovered in China in the 12th century, but far before magnetic bacteria (Italian) (http://it.wikipedia.org/wiki/Batteri_magnetotattici) learned the trick. Magnetotactic bacteria build miniature magnets inside themselves and use them to determine their orientation relative to the Earth's magnetic field [1] (http://www.astronomycafe.net/qadir/ask/a11651.html).