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Nomenclature and classification of the spinel supergroup

Ferdinando Bosi, Cristian Biagioni and Marco Pasero
Nomenclature and classification of the spinel supergroup
European Journal of Mineralogy (October 2018) 31 (1): 183-192

Abstract

A new, IMA-approved classification scheme for the spinel-supergroup minerals is here reported. To belong to the spinel supergroup, a mineral must meet two criteria: (i) the ratio of cation to anion sites must be equal to 3:4, typically represented by the general formula AB (sub 2) X (sub 4) where A and B represent cations (including vacancy) and X represents anions; (ii) its structure must comprise a heteropolyhedral framework of four-fold coordination polyhedra (TX (sub 4) ) isolated from each other and sharing corners with the neighboring six-fold coordination polyhedra (MX (sub 6) ), which, in turn, share six of their twelve X-X edges with nearest-neighbor MX (sub 6) . Regardless of space group, the X anions form a cubic close-packing and each X anion is bonded to three M-cations and one T-cation. The fifty-six minerals of the spinel supergroup are divided into three groups on the basis of dominant X anion: O (super 2-) (oxyspinel), S (super 2-) (thiospinel), and Se (super 2-) (selenospinel). Each group is composed of subgroups identified according to the dominant valence and then the dominant constituent (or heterovalent pair of constituents) represented by the letter B in the formula AB (sub 2) X (sub 4) . The oxyspinel group (33 species) can be divided into the spinel subgroup 2-3 (A (super 2+) B (sub 2) (super 3+) O (super 4) ) and the ulvospinel subgroup 4-2 (A (super 4+) B (sub 2) (super 2+) O (super 4) ), the thiospinel group (20 species) into the carrollite subgroup 1-3.5 (A (super 1+) B (sub 2) (super 3.5+) S (super 4) ) and the linnaeite subgroup 2-3 (A (super 2+) B (sub 2) (super 3+) S (super 4) ), finally, the selenospinel group (3 species) into the bornhardtite subgroup 2-3 (A (super 2+) B (super 3+) (sub 2) Se (sub 4) ) and the potential "tyrrellite subgroup" (A (super 1+) B (sub 2) (super 3.5+) S (super 4) , currently composed by only one species). Once the subgroup is established based on the valence of B, then the mineral species is identified by the combination of the dominant A- and B-cations. Moreover, the present nomenclature redefines the ideal formulae of titanomaghemite, cuprorhodsite, malanite, maghemite, filipstadite, tegengrenite, rhodostannite, toyohaite and xingzhongite as well as discredits "iwakiite", "hydrohetaerolite" and "ferrorhodsite".


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 31
Serial Issue: 1
Title: Nomenclature and classification of the spinel supergroup
Affiliation: Sapienza University of Rome, Department of Earth Sciences, Rome, Italy
Pages: 183-192
Published: 20181009
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 76
Accession Number: 2018-101612
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: Universita di Pisa, ITA, Italy
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201853
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