loadstone n : a permanent magnet consisting of magnetite that possess polarity and has the power to attract as well as to be attracted magnetically [syn: lodestone]
EtymologyFirst attested from 1515, from Middle English lode guide + stone, was used as a guide tool by mariners. See also: lodestar.
Lodestone or loadstone refers to either:
- 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 name "magnet" comes from lodestones found in a place called Magnesia.
In China, the earliest literary reference to magnetism lies in a 4th century BC book called Book of the Devil Valley Master (鬼谷子): "The lodestone makes iron come or it attracts it." The earliest mention of the attraction of a needle appears in a work composed between 20 and 100 AD (Louen-heng): "A lodestone attracts a needle." By the 12th century the Chinese were known to use the lodestone compass for navigation.