Detailed electron-microprobe investigations and crystal-structure determinations established that ‘sartorite’ represents a group of distinct mineral species, each with unique chemistry and crystal structure. These manifest themselves as the 7-, 9- and 11-fold P21/c superstructures of the basic 4.2 Å substructure. Heptasartorite is Tl7Pb22As55S108 [based on 192 atoms per formula unit (apfu), 84Me + 108S] with a = 29.269(2), b = 7.8768(5), c = 20.128(2) Å, β = 102.065(2)° and unit-cell volume V = 4537.8 Å3; enneasartorite is Tl6Pb32As70S140 (based on 248 apfu, 108Me + 140S) with a = 37.612(6), b = 7.8777(12), c = 20.071(3) Å, β = 101.930(2)° and V = 5818.6(15) Å3; hendekasartorite is Tl2Pb48As82S172 (based on 304 apfu, 132Me + 172S) (empirical ΣMe = 132.48) with a = 31.806(5), b = 7.889(12), c = 28.556(4) Å and β = 99.034(2)° with V = 7076.4(15) Å3. Physical and optical properties (grey with metallic lustre, in polished section white with visible bireflectance, red internal reflections; reflectance curves span 28.7–42.5%; Mohs hardness 3–3½) of these phases are very similar so that chemical analysis and/or single-crystal X-ray diffraction is needed to distinguish them. A brief description of complicated AsmSn crank-shaft chains in the walls of double-ribbons which form the As-based slabs of these structures is given. The three new mineral species differ in their structures by 4.2 Å modular increments, not just by cation substitutions. They represent anion-omission derivatives of the ‘ideal’ PbAs2S4 composition with an important role for thallium in charge compensation. The described minerals belong to the late sulfide phases in the Pb–Tl–Ag–As deposit of Lengenbach, Wallis, Switzerland.
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JOURNAL ARTICLE
Heptasartorite, Tl7Pb22As55S108, enneasartorite, Tl6Pb32As70S140 and hendekasartorite, Tl2Pb48As82S172, three members of the anion-omission series of ‘sartorites’ from the Lengenbach quarry at Binntal, Wallis, Switzerland
Dan Topa
Dan Topa
1
Naturhistorisches Museum, Burgring 7, 1010 Wien, Austria*
Corresponding author, e-mail: dan.topa@nhm-wien.ac.at
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Emil Makovicky
Emil Makovicky
2
Department of Geoscience and Resource Management, University of Copenhagen, Østervoldgade 10, 1350 Copenhagen K, Denmark
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Berthold Stoeger
Berthold Stoeger
3
Technische Universität Wien, Karlsplatz 13, 1040 Wien, Österreich
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Chris Stanley
Chris Stanley
4
Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
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European Journal of Mineralogy (2017) 29 (4): 701-712.
Published:
August 01, 2017
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Dan Topa, Emil Makovicky, Berthold Stoeger, Chris Stanley; Heptasartorite, Tl7Pb22As55S108, enneasartorite, Tl6Pb32As70S140 and hendekasartorite, Tl2Pb48As82S172, three members of the anion-omission series of ‘sartorites’ from the Lengenbach quarry at Binntal, Wallis, Switzerland. European Journal of Mineralogy ; 29 (4): 701–712. doi: https://doi.org/10.1127/ejm/2017/0029-2634
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Index Terms/Descriptors
- Binnental
- cell dimensions
- Central Europe
- chemical composition
- crystal structure
- electron probe data
- Europe
- homology
- optical properties
- physical properties
- reflectance
- substitution
- sulfides
- sulfosalts
- Switzerland
- Valais Switzerland
- Lengenbach Quarry
- enneasartorite
- hendekasartorite
- heptasartorite
- sartorite group
Latitude & Longitude