Magnetite is a ferromagnetic material, which is also easily available and possesses considerable magnetic properties. It is a rock mineral and one of the main iron ores, with the chemical formula Fe3O4. It is attracted to a magnet and can be magnetized to become a permanent magnet itself. It is best known for its property of being strongly attracted to magnets.
It is the most commonly mined ore of iron. It is also the mineral with the highest iron content (72.4%). The chemical IUPAC name is iron(II, III) oxide and the common chemical name is ferrous-ferric oxide.
General Information
- Category: Oxide minerals (Spinel structural group)
- Formula: (repeating unit) iron(II,III) oxide, Fe2+Fe3+2O4
- Crystal system: Isometric
- Crystal class: Hexoctahedral (m3m)
- Color: Black, gray with brownish tint in the reflected sun.
Properties
Magnetite is a black, opaque, submetallic to metallic mineral with a Mohs hardness between 5 and 6.5. It is often found in the form of isometric crystals. It is the most strongly magnetic mineral found in nature. It nanoparticles are also thought to form in soils, where they probably oxidize rapidly to maghemite. It is not a component of ordinary rust, although it can form as iron oxidizes in a dry environment.
- Crystal habit: Octahedral, fine granular to massive
- Twinning: On {Ill} as both twin and composition plane, the spinel law, as contact twins
- Cleavage: Indistinct, parting on {Ill}, very good
- Fracture: Uneven
- Tenacity: Brittle
- Mohs scale hardness: 5.5–6.5
- Luster: Metallic
- Streak: Black
- Diaphaneity: Opaque
- Specific gravity: 5.17–5.18
Occurrences
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. Today it is mined as iron ore.
Small grains of magnetite occur in almost all igneous and metamorphic rocks. Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak.
Applications
Due to its high iron content, magnetite has long been a major iron ore. It is reduced in blast furnaces to pig iron or sponge iron for conversion to steel. These pellets are easy to handle and transport by ship, rail, or truck. They can be directly loaded into a blast furnace at a mill and be used to produce iron or steel.
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