Edenharterite (TlPbAs3S6): a new mineral from Lengenbach, Binntal (Switzerland) (original) (raw)

Original paper

Graeser, Stefan; Schwander, Hans

Abstract

Abstract The phase TIPbAs3S6, synthesized in the course of hydrothermal experiments by A. Edenharter (1982), was found as a natural mineral at the well known occurrence of Pb-Tl-Cu-Ag-As-sulphosalt minerals in Lengenbach, Binntal (Switzerland). It occurs in small cavities in Triassic dolomite, together with a large number of other As sulphosalt minerals such as hutchinsonite, hatchite, wallisite, lorandite, and abundant realgar and orpiment. Edenharterite forms euhedral lathlike crystals (less than 1 mm in size), mostly intergrown to aggregates up to 2 - 3 mm. Electron microprobe analysis yielded (mean of 3 analyses): Tl 25.51, Pb 25.08, Sn 0.06, As 27.09, S 23.17, total 100.91 wt %. The simplified formula is close to TIPbAssSô. The mineral is bright brown-black. In thin fragments it is red translucent and has a raspberry-red streak. Microhardness is 98 kg/mm2 (10 g load), corresponding to a Moris hardness of about 2 1/2 - 3, Dcalc = 5.09 g/cm3. Single crystal studies gave an orthorhombic cell with a = 15.465(3), b = 47.507 (8), c = 5.843(2) Å, V = 4292 Å3, space group Fdd2 and Z = 16. The strongest lines in the X-ray powder pattern are (dobs, Us, hkl): 3.801 (100)(191) ; 3.389 (22)(1.11.1) ; 2.901 (19)(3.11.1) ; 2.767 (43)(4.12.0) ; 2.732 (41)(511) ; 2.656 (24)(3.13.1) ; 1.7905 (15)(8.10.0). The name is for Dr. Andreas EDENHARTER (University of Göttingen) who first synthesized the phase TIPbAS3S6 while conducting hydrothermal experiments with Tl-sulphosalts.

Keywords

edenharterite • Tl-Pb-As-sulphosalts • microprobe analyses • single crystal study • formation of Tl-Assulphosalts at Lengenbach • Binntal (Switzerland)