Volume 69 Received 19 December 2012 | |||||||||||
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aDepartment of Geosciences, University of Arizona, Tucson, Arizona 85721-0077, USA, and bLunar and Planetary Laboratory, University of Arizona, 1629 E. University Boulevard, Tucson, AZ 85721-0092, USA
Correspondence e-mail: bschumer@email.arizona.edu
Pirquitasite, ideally Ag2ZnSnS4 (disilver zinc tin tetrasulfide), exhibits tetragonal symmetry and is a member of the stannite group that has the general formula A2BCX4, with A = Ag, Cu; B = Zn, Cd, Fe, Cu, Hg; C = Sn, Ge, Sb, As; and X = S, Se. In this study, single-crystal X-ray diffraction data are used to determine the structure of pirquitasite from a twinned crystal from the type locality, the Pirquitas deposit, Jujuy Province, Argentina, with anisotropic displacement parameters for all atoms, and a measured composition of (Ag1.87Cu0.13)(Zn0.61Fe0.36Cd0.03)SnS4. One Ag atom is located on Wyckoff site Wyckoff 2a (symmetry -4..), the other Ag atom is statistically disordered with minor amounts of Cu and is located on 2c (-4..), the (Zn, Fe, Cd) site on 2d (-4..), Sn on 2b (-4..), and S on general site 8g. This is the first determination of the crystal structure of pirquitasite, and our data indicate that the space group of pirquitasite is I-4, rather than I-42m as previously suggested. The structure was refined under consideration of twinning by inversion [twin ratio of the components 0.91 (6):0.09 (6)].
For related structures in the stannite-kesterite series, see: Orlova (1956
); Hall et al. (1978
); Kissin & Owens (1979
); Bonazzi et al. (2003
). For previous work on hocartite and pirquitasite, see: Johan & Picot (1982
). For details on synthetic stannite group phases, see: Salomé et al. (2012
); Sasamura et al. (2012
); Tsuji et al. 2010
). For other stannite group minerals, see: Chen et al. (1998
); Frenzel (1959
); Garin & Parthé (1972
); Johan et al. (1971
); Kaplunnik et al. (1977
); Kissin & Owens (1989
); Marumo & Nowaki (1967
); Murciego et al. (1999
); Szymanski (1978
); Wintenberger (1979
).
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Data collection: APEX2 (Bruker, 2004
); cell refinement: SAINT (Bruker, 2004
); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008
); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008
); molecular graphics: XtalDraw (Downs & Hall-Wallace, 2003
); software used to prepare material for publication: publCIF (Westrip, 2010
).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2219 ).
We gratefully acknowledge the support of the Arizona Science Foundation and CNPq 202469/2011-5 from the Brazilian Government for MBA. Special thanks go to Dr David Brown for pointing out that bond-valence calculations corroborate the ordering of Cu to the Ag2 site.
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