Wrightite, K2Al2O(AsO4)2, a new oxo-orthoarsenate from the Second scoria cone, Northern Breakthrough, Great Fissure eruption, Tolbachik volcano, Kamchatka peninsula, Russia
| Autor: | Stanislav K. Filatov, Eugeniya Yu. Avdontseva, Svetlana V. Moskaleva, A. P. Shablinskii, Lidyua P. Vergasova |
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| Rok vydání: | 2018 |
| Předmět: |
Cinder cone
geography Materials science Mineral geography.geographical_feature_category 010504 meteorology & atmospheric sciences Fissure Crystal structure 010502 geochemistry & geophysics 01 natural sciences Fumarole Crystallography medicine.anatomical_structure Octahedron Volcano Geochemistry and Petrology medicine Orthorhombic crystal system 0105 earth and related environmental sciences |
| Zdroj: | Mineralogical Magazine. 82:1243-1251 |
| ISSN: | 1471-8022 0026-461X |
| Popis: | The new mineral wrightite, K2Al2O(AsO4)2, was found in 1983 at a fumarole on the Second scoria cone, Northern Breakthrough, Great Fissure eruption, Tolbachik volcano, Kamchatka peninsula, Russia, where it occurs as light yellow aggregates of transparent tabular crystals, with an average size of 0.05 mm × 0.03 mm × 0.005 mm. Wrightite is orthorhombic, space group Pnma, with the unit-cell parameters a = 8.230(5), b = 5.555(4), c = 17.584(1) Å, V = 803.9(6) Å3 and Z = 4 (from powder data). The empirical formula is (K1.69Na0.38)Σ2.07(Al1.80Fe0.24)Σ2.04As1.96O9. The crystal structure (R1 = 0.043) consists of Al2O(AsO4)2 layers in the ab plane with clusters of edge-sharing AlO6 octahedra. Each layer contains two independent isolated AsO4 tetrahedra and two AlO6 octahedra. AlO6 octahedra are linked by edges, forming zigzag chains along the b axis inside the Al–As layer. Eight- and six-coordinated K atoms are located in the interlayer space between Al2O(AsO4)2 layers. The mineral is biaxial (−), α =1.679(2), β =1.685(2), γ (calc.) =1.687; 2V(meas.) = 62(10)° (λ = 589 nm). The strongest lines in the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 8.77(36)(002); 4.458(17)(111); 4.010(19)(201,013); 3.875(19)(104) and 2.972(100)(015). The mineral was named in honour of Adrian Carl Wright, Emeritus Professor at the University of Reading, UK. |
| Databáze: | OpenAIRE |
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