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The crystal structure of jasrouxite, a Pb-Ag-As-Sb member of the lillianite homologous series

Emil Makovicky and Dan Topa
The crystal structure of jasrouxite, a Pb-Ag-As-Sb member of the lillianite homologous series
European Journal of Mineralogy (March 2014) 26 (1): 145-155

Abstract

Jasrouxite, Ag (sub 16) Pb (sub 4) (Sb (sub 25) As (sub 15) ) (sub Sigma 40) S (sub 72) , is triclinic, space group P-1, lattice parameters a = 8.2917(5), b = 19.101(1), c = 19.487(1) Aa, alpha = 89.731(1) degrees , beta = 83.446(1) degrees , and gamma = 89.944(1) degrees . Unit-cell volume is V = 3066.1(3) Aa (super 3) , Z = 1 for the title formula. It is the N =4 member of the lillianite homologous series of modular structures created by unit-cell twinning of (311) slabs of the PbS archetype. The structure contains 30 independent cation sites, from which 12 are mixed sites, and 36 independent sulphur sites (i.e. six times the sites of the lillianite-like subcell). Only the c parameter copies that of lillianite, a is doubled and b is about 3/2 of a diagonal to (001) of lillianite. In agreement with the "2Pb--> Ag + (Sb,As) oversubstitution" against ideal PbAgSb (sub 3) S (sub 6) , the trigonal prismatic sites on composition planes of twinning are occupied by two Pb-Sb rows and one Sb-Sb row, and the PbS-like slabs contain excess number of Ag sites. Unlike lillianite, the alternating (311) (sub PbS) slabs are non-equivalent and each of them has two types of differently occupied diagonal planes of atoms, always present in a 2:1 ratio. This results in triclinic symmetry with only small distortions from monoclinic metrics. In both slab types lone electron pairs of As and Sb congregate in large micelles with elliptic cross-section. Among lillianite homologues, jasrouxite exhibits hitherto unseen complications of cation ordering, resulting from the presence of two distinct metalloids in the structure, oversubstitution by (Ag + M (super 3+) ), and highly expressed lone electron pair activity of trivalent cations.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 26
Serial Issue: 1
Title: The crystal structure of jasrouxite, a Pb-Ag-As-Sb member of the lillianite homologous series
Affiliation: University of Copenhagen, Institute for Geoscience and Natural Resource Management, Copenhagen, Denmark
Pages: 145-155
Published: 201403
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 22
Accession Number: 2014-028693
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
Secondary Affiliation: Naturhistorisches Museum, AUT, Austria
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201418
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