- Lodestone
Lodestone or loadstone refers to either:
*
Magnetite , amagnetic mineral form of iron(II),iron(III) oxide Fe3O4, one of severaliron oxide s.* 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 theEarth's magnetic field . Only magnetite with a particularcrystalline structure , lodestone, can act as a natural magnet and attract and magnetize iron. The name "magnet" comes from lodestones found in a place calledMagnesia .In China, the earliest literary reference to magnetism lies in a
4th century BCE book called "Book of the Devil Valley Master" (鬼谷子): "The lodestone makesiron come or it attracts it."Li Shu-hua, “Origine de la Boussole 11. Aimant et Boussole,” "Isis", Vol. 45, No. 2. (Jul., 1954), p.175] The earliest mention of the attraction of a needle appears in a work composed between 20 and 100 CE ("Louen-heng"): "A lodestone attracts a needle." By the 12th century the Chinese were known to use the lodestone compass for navigation. Also vikings used lodestone for navigation.References
External links
* [http://www.phy6.org/earthmag/lodeston.htm Lodestone]
Wikimedia Foundation. 2010.