Demicheleite-(Cl), BiSCl, a new mineral from La Fossa crater, Vulcano, Aeolian Islands, Italy
-
Francesco Demartin
and
Italo Campostrini
Abstract
Demicheleite-(Cl), ideally BiSCl, is the chlorine analog of demicheleite-(Br) and is closely related to this species that occurs in the same locality. The mineral is the first natural bismuth sulfochloride discovered so far in a natural environment, and it is identical with the corresponding and already known synthetic compound. It was found in an active medium-temperature intracrater fumarole at La Fossa crater, Vulcano Island, Aeolian archipelago, Sicily, Italy. The mineral occurs as acicular to stout translucent crystals up to 0.25 mm long in an altered pyroclastic breccia, together with demicheleite- (Br), bismoclite, bismuthinite, godovikovite, panichiite, and three new minerals pending the IMA approval (IMA 2008-015, IMA 2008-039, and IMA 2008-057). The mineral is orthorhombic, space group Pnam, with a = 7.7933(10), b = 9.9293(12), and c = 3.9880(4) Å, V = 308.60(4) Å3 (from X-ray powder data), Z = 4. The crystal habit is prismatic with {110} as the dominant form, terminated by minor faces of another prism {011}, a pinacoid {010}, and a bipyramid {111}. The color is dark red to black; the luster submetallic. It is non-fluorescent. The tenacity is brittle. The cleavage and fracture were not observed. The calculated density is 5.934 g/cm3.
The chemical analysis obtained by WDS electron microprobe gave (wt%) Bi 72.74, Cl 11.42, Br 3.13, S 11.74, Se 0.01 wt%, total 99.04, corresponding to the empirical formula (based on 3 apfu): Bi0.97(Cl0.90Br0.11)Σ1.01S1.02.
The crystal structure has been refined to a final R index of 0.0218 and contains Bi in sevenfold coordination inside a monocapped trigonal prism. By base sharing, these polyhedra form rows extending along [001]. The rows are connected with symmetry-related rows by sharing S-S edges of the pyramidal caps; these pairs of rows are linked to the others by sharing Cl/Br atoms. The distribution of bond lengths is close to that of the synthetic counterparts BiSCl and BiSBr, with Bi-S distances of 2.601(2) and 2.709(1) Å, and Bi-Cl/Br distances of 2.937(1) and 3.388(1) Å. The strongest 6 lines in the X-ray powder diffraction pattern [dobs(Å) (I) (hkl)] are: 2.896 (100) (121), 4.174 (45) (120), 2.684 (42) (211), 2.784 (33) (201), 1.725 (30) (411), 2.543 (27) (031).
Both the mineral and the mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification of the IMA (no. 2008-020).
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- 27Al NMR spectroscopy at multiple magnetic fields and ab initio quantum modeling for kaolinite
- The effect of oxygen fugacity on the olivine to wadsleyite transformation: Implications for remote sensing of mantle redox state at the 410 km seismic discontinuity
- Spectroscopic characteristics of synthetic olivine: An integrated multi-wavelength and multi-technique approach
- Effects of hydration on thermal expansion of forsterite, wadsleyite, and ringwoodite at ambient pressure
- Forsterite, hydrous and anhydrous wadsleyite and ringwoodite (Mg2SiO4): 29Si NMR results for chemical shift anisotropy, spin-lattice relaxation, and mechanism of hydration
- Structural transitions and electron transfer in coffinite, USiO4, at high pressure
- Fe-Mg partitioning between perovskite and ferropericlase in the lower mantle
- Primitive oxygen-isotope ratio recorded in magmatic zircon from the Mid-Atlantic Ridge
- Determination of the potential for extrinsic color development in natural colorless quartz
- X-ray diffraction and Raman spectroscopic study of clinopyroxenes with six-coordinated Si in the Na(Mg0.5Si0.5)Si2O6-NaAlSi2O6 system
- Phase behavior of protoenstatite at high pressure studied by atomistic simulations
- Metasomatic replacement of inherited metamorphic monazite in a biotite-garnet granite from the Nízke Tatry Mountains, Western Carpathians, Slovakia: Chemical dating and evidence for disequilibrium melting
- Shear viscosity and diffusion in liquid MgSiO3: Transport properties and implications for terrestrial planet magma oceans
- Polarized infrared spectroscopic study of diffusion of water molecules along structure channels in beryl
- The vibrational spectrum of lizardite-1T [Mg3Si2O5(OH)4] at the Γ point: A contribution from an ab initio periodic B3LYP calculation
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- The crystal structure and hydrogen bonding of synthetic konyaite, Na2Mg(SO4)2·5H2O
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- Cathodoluminescence characterization of tridymite and cristobalite: Effects of electron irradiation and sample temperature
- Sequential extraction and DXRD applicability to poorly crystalline Fe- and Al-phase characterization from an acid mine water passive remediation system
- Thermoelasticity of ε-FeSi to 8 GPa and 1273 K
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- Biomineralization associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals
- Evidence for residual elastic strain in deformed natural quartz
- Mineralogy of mine waste at the Vermont Asbestos Group mine, Belvidere Mountain, Vermont
- Structural parameters of chromite included in diamond and kimberlites from Siberia: A new tool for discriminating ultramafic source
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