Spinel group

The spinel group comprises cubic oxide minerals with the general formula AB₂O₄, including spinel, magnetite, and chromite. Its members share a related crystal structure but vary in chemical composition and properties.

Spinel structure: A cubic arrangement of oxygen ions with cations occupying tetrahedral and octahedral sites. This crystal arrangement is the structural basis shared by group members.
Cation ordering: The arrangement of different cations among crystallographic sites in a solid. Different site distributions distinguish spinel-group structures and influence their properties.
Spinel: A magnesium aluminium oxide mineral with the formula MgAl₂O₄. It is the namesake mineral and a representative of the group.
Chromium: A chemical element used chiefly in stainless steel, alloys, and protective coatings. Chromite supplies most of the chromium extracted for industry.
Crystal system: A classification of crystals by their symmetry and lattice geometry. The group belongs to the cubic crystal system.
Oxidation state: A formal measure of an atom’s electron accounting in a compound. Charge balance constrains which cations can occupy sites in AB₂O₄ minerals.
Magnetite: An iron oxide mineral with the formula Fe₃O₄ and strong ferrimagnetism. Its inverse-spinel structure makes it a prominent magnetic group member.
Magnetic recording: The storage of information by encoding it in magnetic states of a material. Ferrite spinels have served as magnetic materials in recording technologies.
Oxide mineral: A mineral composed primarily of oxygen combined with one or more metals. Spinel-group minerals are classified among oxides.
Crystal field theory: A model describing how surrounding ligands split the electronic energy levels of a metal ion. It helps explain color and magnetic behavior arising from transition-metal cations.

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