Lodestone

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) 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].