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Ion substitutions and structural adjustment in Cr-bearing tourmalines

Oleg S. Vereshchagin, Ira V. Rozhdestvenskaya, Olga V. Frank-Kamenetskaya and Anatoly A. Zolotarev
Ion substitutions and structural adjustment in Cr-bearing tourmalines
European Journal of Mineralogy (February 2014) 26 (2): 309-321


The geological settings of Cr-bearing tourmaline occurrences are reviewed and the crystal chemistry of Cr-bearing tourmalines is analysed on the basis of new X-ray single-crystal structure refinements (R 0.019-0.025) of three crystals from the Ural deposits (Cr (sub 2) O (sub 3) content approximately 6 wt.%) and one from Umba Valley, Tanzania ( approximately 1 wt.% Cr (sub 2) O (sub 3) ) and published data (13 structures) on tourmalines from different deposits with Cr content up to 36 oxide wt.%. The boundary between the ordered and the disordered distribution of Cr between Y and Z octahedral sites is determined near 1.03 + or - 0.27 Cr apfu and relationships between Cr content and structural parameters (unit-cell parameters, octahedral bond-lengths, charge of Y and Z sites and polyhedral deformation) are established. An increasing Cr content in tourmaline causes an increase of both lattice parameters, of <Z-O> and <X-O> bond-lengths and a regular variation of the charge of the Y and Z octahedra. In general, the structure becomes less deformed by reducing the distortion of the octahedra and of the tetrahedral ring.

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 26
Serial Issue: 2
Title: Ion substitutions and structural adjustment in Cr-bearing tourmalines
Affiliation: Saint-Petersburg State University, St. Petersburg, Russian Federation
Pages: 309-321
Published: 201402
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 38
Accession Number: 2014-028708
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
S11°40'00" - S01°00'00", E29°30'00" - E40°30'00"
N47°30'00" - N77°30'00", E56°00'00" - E70°00'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201418
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