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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Putirka, Keith / Swainson, Ian

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1945-3027
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Volume 98, Issue 2-3

Issues

Superstructure, crystal chemistry, and cation distribution in filipstadite, a Sb5+-bearing, spinel-related mineral

Paola Bonazzi
  • Corresponding author
  • Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Firenze, Italy
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/ Laura Chelazzi
  • Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Firenze, Italy
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/ Luca Bindi
  • Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Firenze, Italy
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Published Online: 2015-03-07 | DOI: https://doi.org/10.2138/am.2013.4259

Abstract

The crystal structure of the rare, spinel-related Sb mineral filipstadite from Långban, Filipstad district, Värmland, Sweden, has been solved and refined in the space group Fd3̄m [a = 25.9300(6) Å, V = 17434.4(5) Å3, and Z = 216] and refined to R = 4.41% for 681 Fo > 4σ(Fo) using MoKα X-ray data. The structure of filipstadite is topologically identical to the spinel-type structure with cations occupying 1/8 of the tetrahedral (T) and 1/2 of the octahedral (M) interstices of a cubic close-packing of oxygen atoms. Due to the cation ordering, which leads to the tripling of the unit-cell edge, the M and T sites of the spinel-type structure split into six and five independent sites, respectively. Chemical composition was determined by electron microprobe. The fractions of major cations obtained from chemical analysis were distributed between T and M sites taking into account the weighted electron number at both T and M sites, and minimizing the discrepancy between the calculated and the observed overall <M-O> distance. Cations present in minor amounts were assigned on the basis of their known site preference. The obtained populations (2M = Mn2+ 0.56Mg0.76Fe3+0.16Al0.02Sb5+ 0.50; T = Mn2+ 0.60Mg0.07Fe3+0.30 Zn0.02Si4+ 0.01) were then tentatively distributed among the individual M and T sites on the basis of crystal chemical considerations.

Keywords : Filipstadite; spinel; crystal structure determination; superstructure; cation distribution; Långban (Sweden)

About the article

Received: 2012-06-06

Accepted: 2012-09-23

Published Online: 2015-03-07

Published in Print: 2013-02-01


Citation Information: American Mineralogist, Volume 98, Issue 2-3, Pages 361–366, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2013.4259.

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© 2015 by Walter de Gruyter Berlin/Boston.

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