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Argentoliveingite, Ag (sub 3+x) Pb (sub 36-2x) As (sub 51+x) S (sub 112) (0< or =X<0.5), a new homeotype of liveingite from Lengenbach, Binntal, Switzerland, and the crystal chemistry of the liveingite group

Abstract

Argentoliveingite, ideally Ag (sub 3+x) Pb (sub 36-2x) As (sub 51+x) S (sub 112) (0< or =X<0.5), is a new silver-bearing sulphosalt species found in the Lengenbach deposit, Binntal, Canton Wallis, Switzerland. Associated minerals in the holotype, an old museum specimen, are baumhauerite and argentobaumhauerite. In other samples, hendekasartorite, liveingite, rathite and dufrenoysite are present. Argentoliveingite is dark grey and opaque with metallic lustre and a black streak. It is brittle without any discernible cleavage and with conchoidal fracture. In reflected light argentoliveingite is white, pleochroism is not discernible. Red internal reflections are seen on thin edges or at grain boundaries. In crossed polarisers, anisotropism is moderate in dark grey-neutral rotation tints. The reflectance data [R (sub min) , R (sub max) (%), in air] are: 36.6, 41.5 at 470 nm, 34.4, 39.4 at 546 nm, 32.9, 37.8 at 589 nm and 30.7, 35.2 at 650 nm. Mohs hardness is four, microhardness VHN (sub 25) exhibits a range 208-225 kg mm-2, with a mean value of 217 kg mm (super -2) . The average result of 22 electron-microprobe spot analyses for the structurally investigated grain is (in wt%): Ag 2.31(4), Tl 0.35(12), Pb 46.65(26), Sb 0.83(10), As 25.36(14), S 24.27(17), total 99.97(20), corresponding to Ag (sub 3.17) Tl (sub 0.40) Pb (sub 33.31) Sb (sub 1.01) As (sub 50.08) S (sub 112.02) (on the basis of 88Me+112S=200 atoms per formula unit, apfu). The ideal formula is in accordance with the results of the crystal-structure analysis and may be derived from the double ideal liveingite formula, Pb (sub 40) As (sub 48) S (sub 112) , by minor substitution of Sb for As, and the independent, heterovalent [(Ag,Tl) (super +) +(As,Sb) (super 3+) ]<-->2Pb (super 2+) substitution. The density, 5.23 g cm (super -3) , was calculated using the empirical formula. Argentoliveingite is triclinic, space group P1 (no. 2), with a=7.905(2), b=8.469(2), c=137.96(4) Aa, alpha =89.592(2), beta =88.969(2), gamma =89.893(2) degrees , V=9235(5) Aa (super 3) and Z=2. The c axis is double the b axis of liveingite and represents the longest unit-cell parameter for a known natural sulphosalt. The strongest five lines in the (calculated) powder-diffraction pattern are [d in Aa(I)(h,k,l)]: 3.781(85)(2,0,10), 3.668(100)(1,0,33), 3.553(83)(1,0,35), 3.009(91)(1,2,27) and 2.938(94)(1,2,29). Argentoliveingite is a homeotype of liveingite and a new member of the sartorite homologous series with N=3.67, and with a limited extent of the uncoupled substitutions of [Ag (super +) +As (super 3+) ] for 2Pb (super 2+) and [Tl (super +) +As (super 3+) ] for 2Pb (super 2+) . In argentoliveingite the sequence of alternating N=3 and N=4 slabs is different from that in liveingite and is further modified by alternation of three, chemically distinct, types of N=4 slabs. The length and arrangement of crankshaft chains of short As-S bonds differ between different slabs, and especially between the N=4 slabs of liveingite and argentoliveingite. The crystal structures of liveingite and Ag-bearing liveingite (both quantitatively analysed) have been refined for comparison purposes. The uncertain relationship with the phase "rathite-IV" is discussed.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 31
Serial Issue: 5-6
Title: Argentoliveingite, Ag (sub 3+x) Pb (sub 36-2x) As (sub 51+x) S (sub 112) (0< or =X<0.5), a new homeotype of liveingite from Lengenbach, Binntal, Switzerland, and the crystal chemistry of the liveingite group
Affiliation: Naturhistorisches Museum, Vienna, Austria
Pages: 1079-1097
Published: 20190914
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 34
Accession Number: 2019-092932
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N45°21'54" - N45°21'54", E08°13'15" - E08°13'15"
Secondary Affiliation: Universitaet Basel, CHE, SwitzerlandUniversity of Copenhagen, DNK, DenmarkNatural History Museum, GBR, United Kingdom
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201949
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