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 Fd m [a = 25.9300(6) Å, V = 17434.4(5) Å3, 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 theoretical 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+0.30Zn0.02Si4+0.01) were then tentatively distributed among the individual M and T sites on the basis of crystal chemical considerations.

Superstructure, crystal chemistry, and cation distribution in filipstadite, a Sb5+-bearing, spinel-related mineral / Paola Bonazzi; Laura Chelazzi; Luca Bindi. - In: AMERICAN MINERALOGIST. - ISSN 0003-004X. - ELETTRONICO. - 98:(2013), pp. 361-366.

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

BONAZZI, PAOLA;BINDI, LUCA
2013

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 Fd m [a = 25.9300(6) Å, V = 17434.4(5) Å3, 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 theoretical and the observed overall 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+0.30Zn0.02Si4+0.01) were then tentatively distributed among the individual M and T sites on the basis of crystal chemical considerations.
2013
98
361
366
Paola Bonazzi; Laura Chelazzi; Luca Bindi
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/791728
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