Spinel group

The spinels are any of a class of minerals of general formulation AB
2
X
4
which crystallise in the cubic (isometric) crystal system, with the X anions (typically chalcogens, like oxygen and sulfur) arranged in a cubic close-packed lattice and the cations A and B occupying some or all of the octahedral and tetrahedral sites in the lattice.[1][2] Although the charges of A and B in the prototypical spinel structure are +2 and +3, respectively (A2+
B3+
2
X2−
4
), other combinations incorporating divalent, trivalent, or tetravalent cations, including magnesium, zinc, iron, manganese, aluminium, chromium, titanium, and silicon, are also possible. The anion is normally oxygen; when other chalcogenides constitute the anion sublattice the structure is referred to as a thiospinel.

A and B can also be the same metal with different valences, as is the case with magnetite, Fe3O4 (as Fe2+
Fe3+
2
O2−
4
), which is the most abundant member of the spinel group.[3] Spinels are grouped in series by the B cation.

The group is named for spinel (MgAl
2
O
4
), which was once known as "spinel ruby".[4] (Today the term ruby is used only for corundum.)

  1. ^ Robert J. Naumann: Introduction to the Physics and Chemistry of Materials CRC Press, 2008, ISBN 978-1-4200-6134-5. Retrieved 15 April 2018.
  2. ^ H-J Meyer: Festkörperchemie in: H-J Meyer (ed.), Riedel Moderne Anorganische Chemie, Walter de Gruyter, 2012, ISBN 978-3-11-024900-2. Retrieved 15 April 2018.
  3. ^ Ernst, W. G. (1969). Earth Materials (Print ed.). Englewood Cliffs, NJ: Prentice-Hall. p. 58.
  4. ^ "ruby spinel". Encyclopædia Britannica. Retrieved 2022-11-25.

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