Magnetite

Magnetite sample with neodymium magnet

Kristallstruktur Magnetit

HeavyMineralsBeachSand

Magnetite magnetosomes in Gammaproteobacteria

Magnetite-278427

Magnetite-170591

Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe₃O₄. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. It is the most magnetic of all the naturally-occurring minerals on Earth. Naturally-magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism.

Properties

Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5.5–6.5 and a black streak. The crystal system of magnetite is isometric, which means the crystal system has three mutually perpendicular axes of the same length. It commonly forms in octahedral crystals, as well as in the form of granular or massive aggregates.

Formation

Magnetite forms in a variety of geologic settings, from igneous, metamorphic to sedimentary rocks. In igneous rocks, it often crystallizes from a magma with a high iron content. In metamorphic rocks, it can form by the metamorphism of iron-rich sedimentary rocks. In sedimentary rocks, it often forms as layers in banded iron formations. Magnetite can also form in hydrothermal veins. In addition to natural processes, magnetite can be synthetically produced for various industrial applications.

Applications

Magnetite has several important industrial uses. It is a key raw material in the production of steel, where it is used as a source of iron. It is also used in coal washing, and as a medium in dense media separation in mineral processing. Magnetite's magnetic properties make it useful for various forms of magnetic recording and in magnetic nanoparticles for medical imaging techniques.

Environmental and Health Considerations

While magnetite itself is not considered a toxic material, the processing and handling of magnetite can produce dust that may pose health risks if inhaled. In environmental contexts, magnetite plays a role in certain biogeochemical cycles and can influence the magnetic properties of soils and sediments.

See Also

• Iron ore
• Ferrimagnetism
• Lodestone
• Mineral processing