What Mineral Is a Natural Magnet?

Identification

• The mineral magnetite can be attracted to a magnet, and is one of only a few minerals having this characteristic. Its chemical composition is an iron oxide, Fe3O4. Its class is Oxides and Hydroxides and its color is black. Magnetite has two different types of metal ions in two sites in its crystal structure, which causes an electron transfer in a specific path. This electron transfer generates the magnetic field.
  Magnetite is a very common mineral, and is chiefly used as iron ore, with the iron removed from the ore and used to make steel.

Features

• Lodestone is magnetite which has a certain type of crystal structure that has been magnetized and can attract small particles of iron. Although magnetite is common, lodestone is not.
  Magnetite must have a strong magnetic field applied to it in order to become magnetic itself. Scientists believe this occurs naturally when certain types of crystal structures in magnetite are struck by lightning, hitting them with a strong electric current that creates a magnetic field.
  The New Mexico Institute of Technology has tested this theory at their lightning studies laboratory near Socorro, at a mountain which has frequent lightning strikes. The lightning did indeed turn the specific magnetite crystals into magnets -- lodestones.
  Another way that magnetite becomes lodestone is when the minerals are heated past a certain temperature and then cooled back down. This would account for lodestone created during historical and current geologic processes.

Function

• Lodestone has polarity like any magnet, and European explorers navigated their ships with lodestone needle compasses. In fact, the word "lode" came from the Middle English word meaning "way" and apparently was a nickname for this type of magnetite.

History

• But lodestone was discovered long before Middle English developed. It was first discovered in the Magnesia district of Asia thousands of years ago. Ancient Egyptians made records of the mineral, calling it "the bone of Haroeri," after one of the Egyptian gods.
  Geographers have also found some evidence that the Mayan Indians of Central and South America were familiar with lodestone from the way they constructed their ceremonial buildings.

Significance

• At first the Chinese used lodestone for fortune-telling, then around 200 B.C. they invented the compass. This early compass used a spoon-shaped lodestone and they later developed a needle lodestone. The Chinese apparently were the first to use lodestone compasses for navigation on ships.