|Magnetite from the Kola Peninsula, Russia|
|Chemical name||iron(II,III) oxide|
|Crystal habit||Octahedral, fine granular to massive,|
|Mohs Scale hardness||5.5 - 6.5|
|Specific gravity||5.17 - 5.18|
|Lodestone||Magnetic with definite north and south poles|
Magnetite is a valuable source of iron ore. It dissolves slowly in hydrochloric acid.
Distribution of deposits
Magnetite is sometimes found in large quantities in beach sand. Such mineral sands or iron sands or black sands are found in various places such as California and the west coast of New Zealand. The magnetite is carried to the beach via rivers from erosion and is concentrated via wave action and currents.
Large deposits of magnetite are found in Kiruna, Sweden, and in the Adirondack region of New York in the United States. Deposits are also found in Norway, Germany, Italy, Switzerland, South Africa, India, Mexico, and in Oregon, New Jersey, Pennsylvania, North Carolina, Virginia, New Mexico, Utah, and Colorado in the United States. Recently, in June 2005, an exploration company, Cardero Resources, discovered a vast deposit of magnetite-bearing sand dunes in Peru. The dune field covers 250 km2, with the highest dune at over 2000 m above the desert floor. The sand contains 10% magnetite.
Crystals of magnetite have been found in some bacteria (e.g., Magnetospirillum magnetotacticum) and in the brains of bees, of termites, of some birds (e.g., the pigeon), and of humans. These crystals are thought to be involved in magnetoreception, the ability to sense the polarity or the inclination of the earth's magnetic field, and to be involved in navigation. Also, chitons have teeth made of magnetite on their radula making them unique among animals. This means they have an exceptionally abrasive tounge with which to scrape food from rocks.
Preparation as a ferrofluid
- Bluing (steel) is a process in which steel is partially-protected against rust by a layer of magnetite.
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