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.

Additional recommended knowledge

Essential Laboratory Skills Guide

Daily Sensitivity Test

Recognize and detect the effects of electrostatic charges on your balance

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."^[1] 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."^[1] By the 12th century the Chinese were known to use the lodestone compass for navigation.

For some fascinating history of lodestone, see Verschuur's book.^[2]

References

See also

• Magnetism
• Lode Star