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Mineralogical Magazine

Journal of Mineral Science


IMPACT FACTOR 2016: 1.285
5-year IMAPCT FACTOR: 1.553

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Source Normalized Impact per Paper (SNIP) 2016: 0.788

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Volume 81, Issue 1

Issues

The astrophyllite supergroup: nomenclature and classification

Elena Sokolova / Fernando Cámara
  • Dipartimento di Scienze della Terra, Università degli Studi di Torino, via Valperga Caluso 35, I-10125 Torino, Italy
  • Other articles by this author:
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/ Frank C. Hawthorne / Marco E. Ciriotti
  • AMI – Associazione Micromineralogica Italiana, via San Pietro 55, I-10073 Devesi-Ciriè, Italy
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  • De Gruyter OnlineGoogle Scholar
Published Online: 2017-02-24 | DOI: https://doi.org/10.1180/minmag.2016.080.077

Abstract

Here we report a nomenclature and classification for the astrophyllite-supergroup minerals. The HOH block is the main structural unit in all astrophyllite-supergroup structures; it consists of three H-O-H sheets where the T4O12 astrophyllite ribbons occur in the H sheets. In each structure, HOH blocks alternate with I (Intermediate) blocks along [001]. The twelve minerals of the astrophyllite supergroup are divided into three groups based on (1) the type of self-linkage of HOH blocks, i.e. (a) HOH blocks link directly where they share common vertices of D octahedra, or (b) HOH blocks do not link directly; and (2) the dominant cation of the O sheet (the C group: C7 apfu). In the astrophyllite group (HOH blocks connect via D-XPD-D bridges, Fe2+ is dominant at C7), there are six minerals: astrophyllite, niobophyllite, zircophyllite, tarbagataite, nalivkinite and bulgakite. In the kupletskite group (HOH blocks connect via D-XPD-D bridges, Mn2+ is dominant at C7), there are three minerals: kupletskite, niobokupletskite and kupletskite-(Cs). In the devitoite group (HOH blocks do not connect via D-XPD-D bridges), there are three minerals: devitoite, sveinbergeite and lobanovite. The general formula for the astrophyllite-supergroup minerals is of the form A2pBrC7D2(T4O12)2IXOD2XOA4XPDnWA2, where C [cations at the M(1-4) sites in the O sheet] = Fe2+, Mn, Na, Mg, Zn, Fe3+, Ca, Zr, Li; D (cations in the H sheets) = [6,5]Ti, Nb, Zr, Sn4+, [5]Fe3+, Mg, Al; T = Si, minor Al; A2pBrIWA2 (I block) where p = 1,2; r = 1,2; A = K, Cs, Ba, H2O, Li, Rb, Pb2+, Na, □; B = Na, Ca, Ba, H2O, □; I represents the composition of the central part of the I block, excluding peripheral layers of the form A2pBrWA2, e.g. (PO4)2(CO3) (devitoite); XOD = O;XOA = OH, F; XPD = F, O, OH,H2O,□, where n = 0, 1, 2 for (XPD)n; WA=H2O, □.

Keywords: astrophyllite supergroup; nomenclature; classification; ideal formula; astrophyllite; kupletskite and devitoite groups

About the article

Received: 2015-11-09

Accepted: 2016-01-20

Published Online: 2017-02-24

Published in Print: 2017-02-01


Citation Information: Mineralogical Magazine, Volume 81, Issue 1, Pages 143–154, ISSN (Online) 1471-8022, ISSN (Print) 0026-461X, DOI: https://doi.org/10.1180/minmag.2016.080.077.

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© 2017 by Walter de Gruyter Berlin/Boston.

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