Modular structure of highly ordered eudialyte and its place among hydrated minerals of rastsvetaevite family

Journal Article · Sat Jul 15 04:00:00 EDT 2017 · Crystallography Reports

DOI:https://doi.org/10.1134/S1063774517040186· OSTI ID:22758364

Viktorova, K. A.

The crystal structure of a representative of eudialyte group, which was found by A.P. Khomyakov at the Rasvumchorr mountain of the Khibiny alkaline massif (Kola Peninsula), has been studied by X-ray diffraction. The trigonal unit-cell parameters are found to be a = 14.2328(5) Å, c = 60.217(2) Å, V = 10564.08(3) Å3, sp. gr. R3m. The structure has been refined with the isotropic and anisotropic approximation displacement parameters to the total reliability factor R = 5.6%, based on 2989 reflections with |F| > 4σ(F). The idealized formula (Z = 3) is determined as [(H{sub 3}O){sub 11}Na{sub 10}K5]Cа{sub 12}(Na{sub 3}Fe{sub 2}Mn)Si{sub 4}Zr{sub 6}(Si{sub 48}O{sub 144})(OH,Cl){sub 5}(H{sub 2}O){sub 5}. The unit cell of the mineral is doubled due to the presence of two modules of different composition and structure in it (alluaivite-and kentbrooksite-like ones) and the formation of a polyhedral cluster in the kentbrooksite module. A comparison with two hydrated minerals having a modular structure shows that these minerals, being similar in their chemical composition, differ in the cation ordering over the sites of the two modules. The sample under study contains potassium in only one module, while oxonium groups are distributed in both modules but over different sites.

• OSTI ID: 22758364
• Journal Information: Crystallography Reports, Journal Name: Crystallography Reports Journal Issue: 4 Vol. 62; ISSN 1063-7745; ISSN CYSTE3
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ANISOTROPY
CATIONS
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
CRYSTAL STRUCTURE
MODULAR STRUCTURES
POTASSIUM
SILICATE MINERALS
X-RAY DIFFRACTION