IMA 2015-120 = wrightite

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Marco E. Ciriotti
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IMA 2015-120 = wrightite

Messaggio da Marco E. Ciriotti » ven 18 mag, 2018 18:24

Prossima pubblicazione.

Referenza:
▪ Shablinskii, A.P., Filatov, S.K., Vergasova, L.P., Avdontseva, E.Yu., Moskaleva, S.V. (2018): Wrightite, K2Al2O(AsO4)2, a new oxo-orthoarsenate from Great fissure Tolbachik eruption, Kamchatka peninsula, Russia. Mineralogical Magazine, 82, (in press).
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 24833
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: IMA 2015-120 = wrightite

Messaggio da Marco E. Ciriotti » sab 10 nov, 2018 13:39

Referenza:
▪ Shablinskii, A.P., Filatov, S.K., Vergasova, L.P., Avdontseva, E.Yu., Moskaleva, S.V. (2018): Wrightite, K2Al2O(AsO4)2, a new oxo-orthoarsenate from Great fissure Tolbachik eruption, Kamchatka peninsula, Russia. Mineralogical Magazine, 82, (in press).

Abstract:
Wrightite K2Al2O(AsO4)2 is a new mineral species. The specimen was found in 1983 at a fumarole on the Second cinder cone of the Great fissure Tolbachik eruption. Wrightite light yellow aggregates consist of transparent tabular crystals with the average size of 0.05×0.03×0.005 mm3. Space group Pnma, a = 8.230(5), b = 5.555(4), c = 17.584(1) Å, V = 803.9(6) Å3, Z = 4, powder data. The empirical formula is (K1.69Na0.38)Σ2.07(Al1.80Fe0.24)Σ2.04As1.96O9. Crystal structure (R = 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)º (delta = 589 nm). The strongest lines in the X-ray powder diffraction pattern (I-dobs. Å-hkl) are: 36-8.77-002; 17-4.458-111; 19-4.010-201,013; 19-3.875-104; 100-2.972-015. The mineral was named in honour of Adrian Carl Wright, Emeritus Professor at the University of Reading, UK.
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