The systematics of the spinel-type minerals: An overview

Abstract

Compounds with a spinel-type structure include mineral species with the general formula AB 2 φ 4 , where φ can be O 2-, S 2-, or Se 2-. Space group symmetry is Fd3m, even if lower symmetries are reported owing to the off-center displacement of metal ions. In oxide spinels (φ = O 2-), A and B cations can be divalent and trivalent ("2-3 spinels") or, more rarely, tetravalent and divalent ("4-2 spinels"). From a chemical point of view, oxide spinels belong to the chemical classes of oxides, germanates, and silicates. Up to now, 24 mineral species have been approved: ahrensite, brunogeierite, chromite, cochromite, coulsonite, cuprospinel, filipstadite, franklinite, gahnite, galaxite, hercynite, jacobsite, magnesiochromite, magnesiocoulsonite, magnesioferrite, magnetite, manganochromite, qandilite, ringwoodite, spinel, trevorite, ülvospinel, vuorelainenite, and zincochromite. Sulfospinels (φ = S 2-) and selenospinels (φ = Se 2-) are isostructural with oxide spinels. Twenty-one different mineral species have been approved so far; of them, three are selenospinels (bornhardtite, trüstedtite, and tyrrellite), whereas 18 are sulfospinels: cadmoindite, carrollite, cuproiridsite, cuprokalininite, cuprorhodsite, daubréelite, ferrorhodsite, fletcherite, florensovite, greigite, indite, kalininite, linnaeite, malanite, polydymite, siegenite, violarite, and xingzhongite. The known mineral species with spinel-type structure are briefly reviewed, indicating for each of them the type locality, the origin of the name, and a few more miscellaneous data. This review aims at giving the state-of-the-art about the currently valid mineral species, considering the outstanding importance that these compounds cover in a wide range of scientific disciplines.

Raman fingerprint of chromate, aluminate and ferrite spinels

“…[1,2] Spinel-type structure is based on an approximately cubic close packing of anions, with cations hosted within tetrahedrally (T) and octahedrally coordinated (M) sites. In general, A and B cations can reside on both T and M sites, thus giving rise to a variable disorder degree, which can be described using the inversion parameter i, defined as the fraction of the B cations at the T sites.…”

Petrological Features of the Burlakski and Nizhne-Derbinsk Mafic-Ultramafic Plutons (East Sayan Mountains, Siberia, Russia)

“…The chemical composition of chromian spinels from the Burlakski pluton falls within the range of compositions of solid solution between chromite, magnesiochromite, and hercynite [69] (Table S5).…”

Shock history of the fossil ungrouped achondrite Österplana 065: Raman spectroscopy and TEM of relict chrome‐spinel grains

“…Here, we focus on chromite and chrome‐spinel. Chromite (FeCr 2 O 4 ) is an iron‐rich endmember along the solid solution mixing line with magnesioferrite (MgFe 2 O 4 ), where Cr occurs as the major trivalent component with Fe 3+ and Al 3+ as minor components (Biagioni and Pasero ). Chrome‐spinel has the basic formula (Mg, Fe, Mn, Ni) 2+ (Cr, Al, Fe, Mn) 3 2 + O 4 and forms as a solid solution of chromite, spinel (MgAl 2 O 4 ), hercynite (FeAl 2 O 4 ), and magnesiochromite (MgCr 2 O 4 ).…”