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Crystal Structure of Cl-Deficient Analogue of Taseqite from Odikhincha Massif

Journal Article · · Crystallography Reports
 [1];  [2];  [3]
  1. Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)
  2. Russian Academy of Sciences, Vernadsky Institute of Geochemistry and Analytical Chemistry (Russian Federation)
  3. Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” (Russian Federation)
An eudialyte group mineral, found in pegmatites of the Odikhincha massif (the northern part of the Siberian platform), has been investigated using X-ray diffraction, IR spectroscopy, and Raman spectroscopy. The mineral is characterized by a high strontium content and a low chlorine content. It has a trigonal unit cell with the following parameters: a = 14.2700(6) Å and c = 30.057(1) Å; V = 5300.6(1) Å{sup 3}; sp. gr. R3m. The structure has been refined to R = 0.047 in the anisotropic approximation of atomic displacements using 1697F > 4σ(F). The idealized formula (Z = 3) was found to be Na{sub 12}Sr{sub 2}Ca{sub 6}Fe{sub 3}{sup 2+} Zr{sub 3}NbSi{sub 25}O{sub 72}(OH,O){sub 4}Cl(Н{sub 2}О){sub 0.2}. The chemical composition and structure of this mineral are close to those of taseqite; however, it differs from the holotype sample by a low chlorine content and peculiarities of cation distribution over basic structure sites. A comparative analysis of strontium-rich eudialytes has revealed their important crystallochemical feature: selective concentration of strontium in the N4 site. Thus, taseqite, along with heterophyllosilicates, may play a role of strontium concentrator in agpaitic pegmatites.
OSTI ID:
22758247
Journal Information:
Crystallography Reports, Journal Name: Crystallography Reports Journal Issue: 3 Vol. 63; ISSN CYSTE3; ISSN 1063-7745
Country of Publication:
United States
Language:
English