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| Naji, M. |
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| Mohamed, Tarek |
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| Ertürk, Emre |
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Kolitsch, Uwe
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Publications (5/5 displayed)
- 2021Thermessaite-(NH<sub>4</sub>), (NH<sub>4</sub>)<sub>2</sub>AlF<sub>3</sub>(SO<sub>4</sub>), a new fumarole mineral from La Fossa crater at Vulcano, Aeolian Islands, Italycitations
- 2016A single-crystal X-ray and Raman spectroscopic study of hydrothermally synthesized arsenates and vanadates with the descloizite and adelite structure typescitations
- 2011Crystal chemistry of elpidite from Khan Bogdo (Mongolia) and its K- and Rb-exchanged forms
- 2010Hydrogen bonding in coquimbite, nominally Fe2(SO4)3×9H2O, and the relationship between coquimbite and paracoquimbite
- 2009Investigations in the systems Sr-As-O-X (X = H, Cl): Preparation and crystal structure refinements of the anhydrous arsenates(V) Sr3(AsO4)2, Sr2As2O7, a- and ß-SrAs2O6, and of the apatite-type phases Sr5(AsO4)3OH and Sr5(AsO4)3Cl
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article
Thermessaite-(NH<sub>4</sub>), (NH<sub>4</sub>)<sub>2</sub>AlF<sub>3</sub>(SO<sub>4</sub>), a new fumarole mineral from La Fossa crater at Vulcano, Aeolian Islands, Italy
Abstract
<jats:title>Abstract</jats:title><jats:p>Thermessaite-(NH<jats:sub>4</jats:sub>), ideally (NH<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>AlF<jats:sub>3</jats:sub>(SO<jats:sub>4</jats:sub>), is a new mineral found as a medium- to high-temperature (~250–300°C) fumarole encrustation at the rim of La Fossa crater, Vulcano, Aeolian Islands, Italy. The mineral deposited as aggregates of minute (<0.2 mm) sharp prismatic crystals on the surface of a pyroclastic breccia in association with thermessaite, sulfur, arcanite, mascagnite, and intermediate members of the arcanite–mascagnite series.</jats:p><jats:p>The new mineral is colourless to white, transparent, non-fluorescent, has a vitreous lustre, and a white streak. The calculated density is 2.185 g/cm<jats:sup>3</jats:sup>. Thermessaite-(NH<jats:sub>4</jats:sub>) is orthorhombic, space group <jats:italic>Pbcn</jats:italic>, with <jats:italic>a</jats:italic> = 11.3005(3) Å, <jats:italic>b</jats:italic> = 8.6125(3) Å, <jats:italic>c</jats:italic> = 6.8501(2) Å, <jats:italic>V</jats:italic> = 666.69(4) Å<jats:sup>3</jats:sup> and <jats:italic>Z</jats:italic> = 4. The eight strongest reflections in the powder X-ray diffraction data [<jats:italic>d</jats:italic> in Å (<jats:italic>I</jats:italic>)(<jats:italic>hkl</jats:italic>)] are: 5.65 (100)(200), 4.84 (89)(111), 6.85 (74)(110), 3.06 (56)(112), 3.06 (53)(221), 3.08 (47)(311), 2.68 (28)(022) and 2.78 (26)(130). The average chemical composition, determined by quantitative SEM-EDS (N by difference), is (wt.%): K<jats:sub>2</jats:sub>O 3.38, Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> 25.35, SO<jats:sub>3</jats:sub> 36.58, F 26.12, (NH<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>O 22.47, O = F –11.00, total 102.90. The empirical chemical formula, calculated on the basis of 7 anions per formula unit, is [(NH<jats:sub>4</jats:sub>)<jats:sub>1.85</jats:sub>K<jats:sub>0.15</jats:sub>]<jats:sub>Σ2.00</jats:sub>Al<jats:sub>1.06</jats:sub>F<jats:sub>2.94</jats:sub>S<jats:sub>0.98</jats:sub>O<jats:sub>3.06</jats:sub>. The crystal structure, determined from single-crystal X-ray diffraction data [<jats:italic>R</jats:italic>(<jats:italic>F</jats:italic>) = 0.0367], is characterised by corner-sharing AlF<jats:sub>4</jats:sub>O<jats:sub>2</jats:sub> octahedra which form [001] octahedral chains by sharing two <jats:italic>trans</jats:italic> fluoride atoms [Al–F2 = 1.8394(6) Å]. Non-bridging Al–F1 distances are shorter [1.756(1) Å]. The two <jats:italic>trans</jats:italic> oxygen atoms [Al–O = 1.920(2) Å] are from SO<jats:sub>4</jats:sub> tetrahedra. NH<jats:sub>4</jats:sub><jats:sup>+</jats:sup> ions occur in layers parallel to (100) which alternate regularly with (100) layers containing ribbons of corner-sharing AlF<jats:sub>4</jats:sub>O<jats:sub>2</jats:sub> octahedra and associated SO<jats:sub>4</jats:sub> groups. The NH<jats:sub>4</jats:sub><jats:sup>+</jats:sup> ions are surrounded by five oxygen atoms and by four fluorine atoms. The mineral is named as the (NH<jats:sub>4</jats:sub>)-analogue of thermessaite, K<jats:sub>2</jats:sub>AlF<jats:sub>3</jats:sub>(SO<jats:sub>4</jats:sub>), and corresponds to an anthropogenic phase found in the burning Anna I coal dump of the Anna mine, Aachen, Germany. Both mineral and mineral name have been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2011-077).</jats:p>