Structures of orthorhombic and monoclinic Ni3(AsO4)2

Barbier, J.; Frampton, C. S.

doi:10.1107/s0108768191002987

Cited by 8 publications

(2 citation statements)

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“…Xanthiosite is monoclinic, P2 1 /c space group, and has unit cell parameters: a = 5.764, b = 9.559, c = 10.194 Å, β = 92.95°, and V = 560.9 Å 3 . Synthetic orthorhombic polymorph, Cmca space group, with unit-cell parameters: a = 5.943, b = 11.263, c = 8.164 Å, V = 546.5 Å 3 is also known (Barbier and Frampton 1991). The crystal structure of xanthiosite is similar to the structure of olivines and is cation-deficient.…”

Section: Introductionmentioning

confidence: 99%

“…The crystal structure of xanthiosite is similar to the structure of olivines and is cation-deficient. The three-dimensional framework structure is built of NiO 6 octahedra and AsO 4 tetrahedra arranged in layers stacked in the b-axis direction, where Ni octahedra are connected by edges and corners with the As tetrahedra (Barbier and Frampton 1991). However, compared to A 2 BO 4 stoichiometry in the case of olivines, the charge balance is maintained by 1/4 of the available octahedral sites being vacant.…”

Section: Introductionmentioning

confidence: 99%

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Chemical composition and Raman spectroscopy of aerugite, xanthiosite, and a natural analog of KNi3(AsO4)(As2O7) from Johanngeorgenstadt, Germany

Korybska-Sadło¹,

Szuszkiewicz²,

Prell³

et al. 2022

J. Geosci.

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Aerugite Ni 8.5 (AsO 4 ) 2 As 5+ O 8 and xanthiosite Ni 3 (AsO 4 ) 2 , two rare anhydrous arsenates, have been identified in a historic sample from Johanngeorgenstadt, Saxony, Germany. The minerals have been characterized through scanning electron microscopy, electron microprobe analysis and Raman spectroscopy for the first time. They are mostly dark-green (aerugite) to light-green (xanthiosite) fine-grained or microcrystalline crusts on a quartz matrix in association with barite, bunsenite, dolomite, and rooseveltite. Aerugite forms up to 200 μm large pseudo-hexagonal platy crystals, whereas xanthiosite forms short prisms to nearly equant forms, often with indistinct, poorly-developed and rounded faces. The chemical composition of the two minerals can be expressed by the empirical formulas: (Ni 7.92 Co 0.52 Cu 0.06 ) Σ8.50 (As 1.00 O 4 ) 2 As 1.00 O 8 with traces of Bi (aerugite, mean of 4 analyses, based on 32 oxygens) and (Ni 2.85 Co 0.12 Cu 0.03 ) Σ3.00 (As 1.00 O 4 ) 2 (xanthiosite, mean of 5 analyses, based on 32 oxygens). The Raman spectra of both minerals lack bands related to OH stretching vibrations and are dominated by antisymmetric ν 3 and symmetric ν 1 As-O vibrations in AsO 4 polyhedra centered at 817, 846 and 886 cm -1 in the case of aerugite and at 786, 808, 826 and 843 cm -1 in xanthiosite. Bands from stretching vibrations As-O in AsO 4 polyhedra are located at 728 and 735 cm -1 in aerugite and are slightly displaced to 726 and 747 cm -1 in xanthiosite. The Raman spectrum of aerugite also contains well-defined 692, 675 and 658 cm -1 bands due to the stretching mode of NiO 6 octahedra, a broad feature at 576 cm -1 probably from a number of modes connected with AsO 6 octahedra. On the other hand, the xanthiosite spectrum displays a number of low-intensity, well-defined bands related to antisymmetric ν 4 and ν 2 symmetric bending vibrations in AsO 4 below 700 cm -1 as well as to lattice vibrational modes and Ni-O interactions below 250 cm -1 . Locally, the interstices between xanthiosite grains are filled with cryptocrystalline mass with the mean chemical composition of (K 0.90 Ba 0.01 ) Σ0.91 (Ni 2.86 Co 0.11 Cu 0.05 ) Σ3.02 (As 1.00 O 4 )(As 2.1 O 7 ) with traces of Na (mean of 7 analyses, based on 11 oxygens). The recorded Raman spectrum, with a strongly overlapping xanthiositerelated signal, lacks bands of water molecules or OH groups and contains bands related to the As-O-As vibration modes attributed to pyroarsenate As 2 O 7 groups. Although it was impossible to obtain more detailed data on crystal structure, we suggest this is the first reported natural occurrence of KNi 3 (AsO 4 )(As 2 O 7 ) phase.Keywords: aerugite, xanthiosite, KNi 3 (AsO 4 )(As 2 O 7 ), arsenates, chemistry, Raman spectroscopy

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemical composition and Raman spectroscopy of aerugite, xanthiosite, and a natural analog of KNi3(AsO4)(As2O7) from Johanngeorgenstadt, Germany

Korybska-Sadło¹,

Szuszkiewicz²,

Prell³

et al. 2022

J. Geosci.

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Ein Beitrag über ein cobaltreiches Oxoarsenat/‐vanadat: Co₅AsVO₁₀

Osterloh

Müller‐Buschbaum

1994

Zeitschrift anorg allge chemie

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Einkristalle von Co5AsVO10 wurden durch Feststoffreaktionen erhalten und röntgenographisch untersucht. Diese Verbindung kristallisiert mit monokliner Symmetrie, Raumgruppe C 2h3–C2/m; a = 19,134; b = 6,095; c = 17,482 Å; β = 133,37°; Z = 8. Der neue Strukturtyp ist durch CoO6‐ und AsO6‐Oktaederschichten ausgezeichnet, die teilweise alternierend mit Co2+ und As5+ besetzt sind. Die Oktaederschichten werden durch Co2+ in tetraedrischer Koordination und statistisch mit V5+ und As5+ besetzte Punktlagen verknüpft.

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