La pirquitasite, Ag2ZnSnS4, un nouveau membre du groupe de la stannite

Abstract

La pirquitasite, Ag₂ZnSnS₄, quadratique, I[-4]2m ou I[-4], a = 5,786, c = 10,829 Å, à structure type stannite, a été découverte dans le gisement de Pirquitas (Argentine), en association avec hocartite, pyrite, marcasite, wurtzite, franckéite, miargyrite, aramayoïte, chalcostibite, stannite, kësterite, rhodostannite et cassitérite. En lumière réfléchie, elle est gris brunâtre ; macles polysynthétiques, anisotropie forte du rouge brique au vert clair. Réflexions internes rouges. Microdureté Vickers : 218 kg/mm² (P = 25 g). Raies les plus intenses du diagramme de poudre : 3,267 (10) (112), 2,901 (4) (200), 2,049 (6) (220), 1,976 (8) (204), 1,735(8) (132), 1,289 (4) (240), 1,165 (4) (244). Pouvoir réflecteur (Rmax et Rmin) : 24,6 — 21,7(420), 23,8 — 21,8(500), 24,1 — 22,2 (540), 24,1 — 22,9 (600), 21,6 — 20,1 (700 nm). Elle forme une solution solide très étendue (12 à 67 % mol.) avec la hocartite. On observe une immiscibilité de la hocartite avec la stannite. La rhodostannite de Pirquitas forme une solution solide avec le terme extrême Ag₂FeSn₃S₈ jusqu'à la composition (Ag₁,₁₄₃ Cu₀,₈₉₉)₂,₀₄₂ Fe₀,₉₉₆ S₃,₀₁₄ S₇,₉₄₆. Les propriétés optiques de cette phase sont données.

Mineral chemistry of In-bearing minerals in the Santa Fe mining district, Bolivia

“…Greisens result from complex metasomatic processes that affect and take place within a nearly granitic mass and the adjacent country rocks (Pirajno, 2009). Hall et al (1978) Sakuraiite 10 (Cu,Zn,Fe) 3.2 (In,Sn) 0.8 S 4.0 (Cu,Zn,Fe) 3 (In,Sn)S 4 Shimizu et al (1986) Hocartite 3 Ag 1.9 Fe 06 Zn 0.2 Cu 0.1 Sn 1.0 S 4.0 Ag 2 FeSnS 4 Fleischer (1969) Pirquitasite 2 Ag 1.9 Zn 0.9 Sn 1.0 S 4.0 Ag 2 ZnSnS 4 Johan and Picot (1982) Petrukite 7 (Cu,Ag) 1.95 (Fe,Zn) 1.2 (Sn,In) 0.98 S 4.0 (Cu,Ag) 2 (Fe,Zn)(Sn,In)S 4 Petruk (1973) Franckeite Group Franckeite Frondel (1943) The genesis of a greisen deposit includes an early alkaline stage, a greisen stage itself and a late veining stage. Silicification is common in greisen alteration, evidenced by the common quartz flooding of the greisen altered rocks (Shcherba, 1970).…”

Pirquitasite, Ag2ZnSnS4

“…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).…”

“…Pirquitasite is a member of the stannite group of tetragonal sulfides, which exhibit space group I42m or I4, and is an ordered derivative of the sphalerite structure (Johan and Picot, 1982). The stannite group currently contains thirteen species (Table 1), of which only kësterite, ferrokësterite, and pirquitasite are known to display space group I4.…”

“…Pirquitasite was first described by Johan and Picot (1982), from the Pirquitas deposit, Argentina, as a silver zinc tin sulfide with ideal chemical formula Ag 2 ZnSnS 4 and a stannite-like structure. An extensive solid solution between hocartite (Ag 2 FeSnS 4 ) and pirquitasite was described by Johan and Picot (1982).…”

“…Pirquitasite was first described by Johan and Picot (1982), from the Pirquitas deposit, Argentina, as a silver zinc tin sulfide with ideal chemical formula Ag 2 ZnSnS 4 and a stannite-like structure. An extensive solid solution between hocartite (Ag 2 FeSnS 4 ) and pirquitasite was described by Johan and Picot (1982). Because of the solid solution and the I42m symmetry attributed to hocartite, Johan and Picot (1982) proposed that pirquitasite also exhibits I42m symmetry.…”