title: Structure of Pb-rich chabournéite from Jas Roux, France.
abstract: The crystal structure of a specimen of `Pb-rich' chabournéite from Jas Roux, Hautes-Alpes, France, with the chemical formula obtained by electron microprobe analysis of Ag(0.04 (1))Tl(2.15 (2))Pb(0.64 (1))Sb(5.12 (1))As(5.05 (1))S(17.32 (5)), has been solved by X-ray single-crystal diffraction on the basis of 36,550 observed reflections (with F(o) > 4σF(o)) with a final R1 = 0.074. Pb-rich chabournéite is triclinic P1, with unit-cell parameters a = 8.5197 (4), b = 42.461 (2), c = 16.293 (8) Å, α = 83.351 (2), β = 90.958 (2), γ = 84.275 (2)°, V = 5823 (3) Å(3). Its structural formula is close to [Tl2(Pb(0.8)Tl(0.1)Sb(1.1))](Sb(4.1)As(4.9))S17, with Z = 8. Its crystal structure is formed by the alternation of two pairs of slabs along the b axis, deriving from the SnS and PbS archetypes, respectively. 104 independent cation sites and 136 S sites occur in the unit cell. Slab interfaces show the alternation, along c, of Tl sites, ninefold coordinated, with Pb, Sb or mixed/split (Pb,Sb) and (Pb,Tl) sites. Within the slabs, 72 independent M(3+) sites (M(3+) = As, Sb) occur. Considering M(3+)-S bond distances shorter than 2.70 Å, MS3 triangular pyramidal groups are condensed according to various M(m)S(n) chain fragments (`polymers'). The solution of the crystal structure of chabournéite allows its comparison with the closely related homeotypes protochabournéite and dalnegroite.
authors: Dipartimento di Scienze della Terra, Università di Pisa, Via Santa Maria 53, I-56126 Pisa, Italy.
authors: Cristian
authors: C
authors: Biagioni
authors: Institut des Matériaux Jean Rouxel, UMR 6502, CNRS, Université de Nantes, 2 rue de la Houssinière, 44 322 Nantes CEDEX 3, France.
authors: Yves
authors: Y
authors: Moëlo
authors: 421 avenue Jean Monnet, 13090 Aix-en-Provence, France.
authors: Georges
authors: G
authors: Favreau
authors: 24 rue Mozart, 93160 Noisy-le-Grand, France.
authors: Vincent
authors: V
authors: Bourgoin
authors: Collection des minéraux de l'UPMC-Sorbonne Universités, case courrier 73, 4 place Jussieu, 75252 Paris CEDEX 5, France.
authors: Jean-Claude
authors: JC
authors: Boulliard
keywords: chabournéite; geochemical behavior; homeotypes; hydrothermal ore deposits