New Data on Isomorphism in Eudialyte-Group Minerals. I. Crystal Structure of Titanium-Rich Eudialyte from the Kovdor Alkaline Massif

Journal Article · Sun Jul 15 04:00:00 EDT 2018 · Crystallography Reports

DOI:https://doi.org/10.1134/S1063774518040223· OSTI ID:22758221

Chukanov, N. V. ^[1]; Viktorova, K. A.

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1. Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)

An abnormally titanium-rich mineral of the eudialyte group was studied by IR spectroscopy and X-ray diffraction. The trigonal unit cell parameters are a = 14.165(1) Å, c = 30.600(5) Å, V = 5317.23(4) Å{sup 3}, sp. gr. R3m. The crystal structure was refined to R = 0.034 with anisotropic displacement parameters using 2530 reflections with F > 3σ(F). The idealized formula of the mineral (Z = 3) is Na{sub 8}(H{sub 3}O){sub 5}(K,Ce,Sr){sub 2}Ca{sub 6}Zr{sub 2}Ti{sub 1.2}(Fe,Mn){sub 0.6}Si{sub 26}O{sub 72}(OH){sub 2}Cl · 4H{sub 2}O. At the ratio Zr: Ti ~ 2: 1, titanium atoms lie in four sites and are not predominant in any of them. Another distinguishing feature of the mineral is the structural separation of chemical elements, such that K, Sr, and Ce cations and H{sub 3}O groups are randomly distributed between four split sites to form polyhedra with different volumes. The isomorphism of Zr and Ti in eudialyte-group minerals is discussed.

• OSTI ID: 22758221
• Journal Information: Crystallography Reports, Journal Name: Crystallography Reports Journal Issue: 4 Vol. 63; ISSN 1063-7745; ISSN CYSTE3
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ANISOTROPY
ATOMS
CATIONS
CERIUM
CRYSTAL STRUCTURE
INFRARED SPECTRA
POTASSIUM
SILICATE MINERALS
STRONTIUM
TITANIUM
X-RAY DIFFRACTION