Magnetite

Magnetite is a naturally occurring iron oxide mineral with the formula Fe₃O₄. Its strong magnetism makes it distinctive among common minerals and useful as an iron ore.

Inverse spinel structure: A crystal arrangement in which cations occupy both tetrahedral and octahedral sites, with a characteristic distribution between them. Magnetite’s iron ions occupy both kinds of site in this structure.
Iron oxide: A chemical compound composed of iron and oxygen, occurring in minerals, rust, and industrial materials. Magnetite is one member of this family of compounds.
Iron ore: A naturally occurring material from which metallic iron can be extracted economically. Magnetite is a major iron ore because it contains abundant iron and can be magnetically concentrated.
Lodestone: A naturally magnetized piece of magnetite that can attract iron and align with Earth’s magnetic field. Lodestone is magnetite whose persistent magnetization is strong enough to be noticed directly.
Hematite: An iron oxide mineral with the formula Fe₂O₃, commonly red to steel-gray and an important iron ore. Unlike magnetite, hematite is not strongly ferrimagnetic under ordinary conditions.
Ferrimagnetism: Magnetic order in which oppositely directed magnetic moments do not cancel, leaving a net magnetization. Unequal opposing iron-ion moments give magnetite its strong net magnetization.
Oxidation state: A formal accounting of electron distribution that assigns an apparent charge to an atom in a compound. Magnetite contains iron in both +2 and +3 oxidation states.
Magnetic separation: A process that separates magnetic materials from nonmagnetic ones using a magnetic field. Its strong magnetism allows magnetite ore to be separated from much waste rock.
Banded iron formation: An ancient sedimentary rock made of alternating iron-rich and silica-rich layers. Magnetite is a common iron-bearing mineral in these major iron deposits.
Maghemite: A ferrimagnetic iron oxide with a structure closely related to magnetite and an approximate formula of γ-Fe₂O₃. Maghemite resembles magnetite but contains predominantly iron in the +3 oxidation state.

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