Crystal structure and genesis of the hydrated analog of rastsvetaevite

Journal Article · Sun Nov 15 04:00:00 EST 2015 · Crystallography Reports

DOI:https://doi.org/10.1134/S1063774515060279· OSTI ID:22645531

Aksenov, S. M.; Rozenberg, K. A. ^[1]

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1. Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

The crystal structure of the hydrated analog of the mineral rastsvetaevite (tentatively called “hydrorastsvetaevite”), which was found by A.P. Khomyakov in ultraagpaitic pegmatites at the Rasvumchorr Mountain of the Khibiny alkaline massif (Kola Peninsula), has been determined by single crystal X-ray diffraction. The trigonal unit-cell parameters are as follows: a = 14.2812(2) Å, c = 60.533(5) Å, V = 10691.54(3) Å{sup 3}, sp. gr. R3m. The structure was refined to R = 5.9% in the isotropic and anisotropic approximation of atomic displacement parameters based on 2068 ref lections with |F| > 3σ(F). “Hydrorastsvetaevite” is on the whole analogous to other 24-layer representatives of the eudialyte group (called “megaeudialytes”), but is characterized by a high potassium content and is distinguished from other potassium-rich minerals (rastsvetaevite, davinciite, and andrianovite) by low sodium and alkaline-earth metal content, as well as by a high degree of hydration accompanied by the insertion of H{sub 3}O groups, which partially or completely replace large cations. The idealized formula of “hydrorastsvetaevite” (Z = 3) is (Na{sub 11}(H{sub 3}O){sub 11}K{sub 6}(H{sub 2}O){sub 1.5}Sr)Ca{sub 12}Fe{sub 3}Na{sub 2}MnZr{sub 6}Si{sub 52}O{sub 144}(OH){sub 4.5}C{sub l3.5}(H{sub 2}O){sub 0.5}. In alkaline pegmatites, “hydrorastsvetaevite” occurs as a secondary mineral developed from the original rastsvetaevite through decationation and hydration. The characteristic features of the genesis of eudialyte-group minerals containing potassium as a species-forming cation are discussed in terms of the concept of transformational mineral species.an]Mis||Original Russian Text © R.K. Rastsvetaeva, S.M. Aksenov, K.A. Rozenberg, 2015, published in Kristallografiya, 2015, Vol. 60, No. 6, pp. 897–905.

• OSTI ID: 22645531
• Journal Information: Crystallography Reports, Journal Name: Crystallography Reports Journal Issue: 6 Vol. 60; ISSN CYSTE3; ISSN 1063-7745
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METALS
ATOMIC DISPLACEMENTS
MONOCRYSTALS
PEGMATITES
POTASSIUM
SILICATE MINERALS
TRIGONAL LATTICES
X-RAY DIFFRACTION