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Ecrinsite, AgTl (sub 3) Pb (sub 4) As (sub 11) Sb (sub 9) S (sub 36) , a new thallium-rich homeotype of baumhauerite from the Jas Roux sulphosalt deposit, Parc National des Ecrins, Hautes-Alpes, France

Dan Topa, Uwe Kolitsch, Emil Makovicky and Chris J. Stanley
Ecrinsite, AgTl (sub 3) Pb (sub 4) As (sub 11) Sb (sub 9) S (sub 36) , a new thallium-rich homeotype of baumhauerite from the Jas Roux sulphosalt deposit, Parc National des Ecrins, Hautes-Alpes, France
European Journal of Mineralogy (June 2017) 29 (4): 689-700

Abstract

Ecrinsite, ideally AgTl (sub 3) Pb (sub 4) As (sub 11) Sb (sub 9) S (sub 36) , is a new thallium sulphosalt species found in the Jas Roux As-Sb-Pb-Tl-Hg-Ag deposit, Parc National des Ecrins, Departement des Hautes-Alpes, France. Associated minerals in four different samples are jasrouxite, stibnite, smithite, guettardite, chabourneite, pierrotite and As-bearing zinkenite. Ecrinsite is opaque with metallic lustre. It is brittle without any discernible cleavage and with conchoidal fracture. In reflected light ecrinsite is white, pleochroism is not discernible. Internal reflections are absent. In crossed polarisers, anisotropism is distinct, with rotation tints in shades of grey. The reflectance data (%, air) are: 37.3, 38.6 at 470 nm, 35.2, 36.7 at 546 nm, 34.0, 35.5 at 589 nm and 32.0, 33.3 at 650 nm. Mohs hardness is 3-31/2, microhardness VHN (sub 25) is in the range 175-201, with a mean value of 189 kg mm (super -2) . Average results of 20 electron-microprobe analyses for the structurally investigated grain are (in wt%): Ag 2.03(10), Cu 0.02(1), Tl 14.57(20), Pb 16.23(32), Sb 23.97(25), As 17.87(17), S 25.20(15), total 99.88 (15), corresponding to Ag (sub 0.87) Cu (sub 0.02) Tl (sub 3.28) Pb (sub 3.61) Sb (sub 9.06) As10.98S36.19 (on the basis of 28Me + 36S = 64 apfu). The simplified formula, AgTl (sub 3) Pb (sub 4) Sb (sub 9) As (sub 11) S (sub 36) , is in accordance with the results of the crystal-structure analysis and may be derived from the ideal baumhauerite formula, Pb (sub 12) As (sub 16) S (sub 36) , by substitution of Sb for As and [(Tl,Ag) (super +) + (As,Sb) (super 3+) ] <--> 2Pb (super 2+) . The density, 4.96 g cm (super -3) , was calculated using the ideal formula. Ecrinsite has a triclinic cell, space group P1, with a = 8.080(2), b = 8.533(2), c = 22.613(4) A, alpha = 90.23(3) degrees , beta = 97.17 (3) degrees , gamma = 90.83(3) degrees , V = 1546.7(6) A (super 3) , and Z = 1. The strongest five lines in the (calculated) powder-diffraction pattern are [d in A(I)(h k l)]: 4:14(68) (1 0 5), 3.72(92)(105), 3:56(100)(1 0 6) 3:53(80)(1 2 2) and 3.48(72)(122). Ecrinsite is a new member of the sartorite homologous series with N (sub 1,2) = 3, 4, i.e., N = 3.5. Four other members share the same N value as ecrinsite: baumhauerite, argentobaumhauerite, boscardinite and bernarlottiite. By comparison to the closely related boscardinite (ideally Tl (sub 2) Pb (sub 8) Sb (sub 14) As (sub 4) S (sub 36) ), ecrinsite is characterised by both an excess of As over Sb and a distinctly higher substitution of [(Tl,Ag) (super +) +(As,Sb) (super 3+) ] <--> 2Pb (super 2+) Baumhauerite and bernarlottiite are basically unsubstituted members, whereas argentobaumhauerite has a Ag substitution, without Tl.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 29
Serial Issue: 4
Title: Ecrinsite, AgTl (sub 3) Pb (sub 4) As (sub 11) Sb (sub 9) S (sub 36) , a new thallium-rich homeotype of baumhauerite from the Jas Roux sulphosalt deposit, Parc National des Ecrins, Hautes-Alpes, France
Affiliation: Naturhistorisches Museum, Vienna, Austria
Pages: 689-700
Published: 20170608
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 23
Accession Number: 2017-082583
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 10 tables
N44°48'45" - N44°48'45", E06°19'18" - E06°19'18"
Secondary Affiliation: University of Copenhagen, DNK, DenmarkNatural History Museum, GBR, United Kingdom
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201743
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