The Structure of Antimonian Dussertite and the Role of Antimony in Oxysalt Minerals

U. Kolitsch1, P. G. Slade2, E. R. T. Tiekink3 and A. Pring1
1 Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, S. A. 5000, Australia
2 CSIRO Land and Water, Private Bag No. 2, Glen Osmond, S. A. 5064, Australia
3 Department of Chemistry, The University of Adelaide, Australia 5005

Abstract: The structure of antimonian dussertite, Ba(Fe0.843+,Sb0.165+)3(AsO4)2(OH,H2O)6, has been refined in space group R¯3m with a 7.410(3), c 17.484(4) Å, Z = 3, to R = 3.2 % and Rw = 3.7 % using 377 observed reflections with I ⩾ 3 σ(I). The structure is of the alunite-type and consists of sheets of corner-sharing (Fe3+,Sb5+)O6 octahedra parallel to (0001). The substitution of Sb5+ for Fe3+ and not for As5+, is unambiguously demonstrated not only by the structure refinement but also by electron microprobe analyses and crystal-chemical considerations. The icosahedrally coordinated Ba cations occupy cavities between pairs of octahedral sheets and are surrounded by six O atoms from the AsO4 tetrahedra and six O atoms from the (Fe3+,Sb5+)O6 octahedra. The mean bond lengths for the various coordination polyhedra are As-O 1.684(3) Å, (Fe,Sb)-O 2.004(1) Å,, and Ba-O 2.872(2) Å. A hydrogen-bonding network is modelled using bond-valence calculations. The dussertite sample investigated is the first member of the crandallite group found to contain substantial Sb.

Keywords: dussertite • crystal structure • crystal chemistry • antimony • crandallite group

Mineralogical Magazine; February 1999 v. 63; no. 1; p. 17-26; DOI: 10.1180/002646199548277
© 1999, The Mineralogical Society
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