Fassinaite, Pb22+(S2O3)(CO3), the first mineral with coexisting thiosulphate and carbonate groups:d escription and crystal structure
- Author(s)
- Luca Bindi, Fabrizio Nestola, Uwe Kolitsch, Alessandro Guastoni, F. Zorzi
- Abstract
Fassinaite, ideally Pb22+(S2O3)(CO3), is a new mineral from the Trentini mine, Mount Naro, VicenzaProvince, Veneto, Italy (holotype locality). It is also reported from the Erasmus adit, SchwarzleoDistrict, Leogang, Salzburg, Austria and the Friedrich-Christian mine, Schapbach, Black Forest, Baden-Wu¨rttemberg, Germany (cotype localities). At the Italian type locality it occurs as acicular [010],colourless crystals up to 200 mm long, closely associated with galena, quartz and anglesite. At theAustrian cotype locality it is associated with cerussite, rare sulphur and very rare phosgenite. At theGerman cotype locality anglesite is the only associated phase. Fassinaite crystals commonly have flatchisel-shaped terminations. They are transparent with vitreous to adamantine lustre and a white streak.Fassinaite is brittle with an irregular fracture and nodiscernible cleavage; the estimated Mohs hardnessis 1D_2. The calculated density for the type material is 6.084 g cm_3 (on the basis of the empiricalformula), whereas the X-ray density is 5.947 g cm_3. In common with other natural lead thiosulphates(i.e. sidpietersite and steverustite) fassinaite has intense internal reflections, which do not allowsatisfactory optical data to be collected; the crystals are length-slow and have very high birefringence.The mineral is not fluorescent.Fassinaite is orthorhombic, space group Pnma, with unit-cell parameters (for the holotype material)a = 16.320(2), b = 8.7616(6), c = 4.5809(7) A ° , V = 655.0(1) A ° 3, a:b:c = 1.863:1:0.523, Z = 4. Singlecrystalstructural studies were carried out on crystals from all three localities: R1(F) values rangebetween 0.0353 and 0.0596. The structure consists of rod-like arrangements of Pb-centred polyhedrathat extend along the [010] direction. These ‘rods’ are linked, alternately, by (CO3)2_ and (S2O3)2_groups. The (S2O3)2_ groups point alternately left and right (in a projection on [001] with [010] setvertical) if the apex occupied by the S2_ in the thiosulphate group is defined to be the atom giving thedirection. The lead atoms are nine-coordinated by seven oxygen atoms and two sulphur (S2_) atoms.The eight strongest X-ray powder-diffraction lines [d in A ° (I/I0) (hkl)] are: 4.410 (39) (101), 4.381 (59)(020), 4.080 (62) (400), 3.504 (75) (301), 3.108 (100) (121), 2.986 (82) (420), 2.952 (49) (221) and2.736 (60) (321). Electron-microprobe analyses produce an empirical formula Pb2.01(1)(S1.82(2)O3)CO3(on the basis of six oxygen atoms). The presence of both carbonate and thiosulphate groups wascorroborated by Raman spectra, which are discussed in detail. Fassinaite is named after Bruno Fassina(b. 1943), an Italian mineral collector who discovered the mineral in 2009.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- University of Florence, University of Padova, Museum of Natural History
- Journal
- Mineralogical Magazine
- Volume
- 75
- Pages
- 2721-2732
- No. of pages
- 12
- ISSN
- 0026-461X
- Publication date
- 2011
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105113 Crystallography, 104006 Solid state chemistry, 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/b65420d9-7ef7-41be-8206-ff418aee4522