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Trabzonite, Ca (sub 4) [Si (sub 3) O (sub 9) (OH)]OH; crystal structure, revised formula, new occurrence and relation to killalaite

T. Armbruster, B. Lazic, I. O. Galuskina, E. V. Galuskin, E. Gnos, K. M. Marzec and V. M. Gazeev
Trabzonite, Ca (sub 4) [Si (sub 3) O (sub 9) (OH)]OH; crystal structure, revised formula, new occurrence and relation to killalaite
Mineralogical Magazine (June 2012) 76 (3): 455-472

Abstract

The crystal structure of the rare skarn mineral trabzonite, Ca (sub 4) [Si (sub 3) O (sub 9) (OH)]OH, from the type locality near Ikizdere, Turkey and from the Upper Chegem caldera, Northern Caucasus, Kabardino-Balkaria, Russia has been solved and refined using single-crystal X-ray data. This shows that the chemical formula should be modified from Ca (sub 4) (Si (sub 3) O (sub 10) ).2H (sub 2) O, reported in the original trabzonite description, to an OH-bearing composition. The crystal structure, which contains Si (sub 3) O (sub 10) trimers embedded in a framework of CaO (sub 6-8) polyhedra, has orthorhombic symmetry, space group Ama2, a = 20.6, b = 9.1, c = 10.3 Aa. The orthorhombic A-centred cell is easily obtained by transformation from the original monoclinic cell of P2 (sub 1) /m symmetry. The revised formula means that trabzonite and foshagite are polymorphs; foshagite has wollastonite-like silicate chains and in contrast to trabzonite it does not contain silanol groups. The structure and composition of killalaite from both localities was also studied. Single-crystal X-ray structure refinement of killalaite from the Northern Caucasus confirmed it to be non-stoichiometric with a composition between Ca (sub 6) [Si (sub 2) O (sub 6) (OH)] (sub 2) (OH) (sub 2) and Ca (sub 7) [Si (sub 2) O (sub 7) ] (sub 2) (OH) (sub 2) (Z = 2). Trabzonite, killalaite and dellaite form a series of modular structures which differ mainly in the degree of condensation of the SiO (sub 4) units.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 76
Serial Issue: 3
Title: Trabzonite, Ca (sub 4) [Si (sub 3) O (sub 9) (OH)]OH; crystal structure, revised formula, new occurrence and relation to killalaite
Affiliation: University of Bern, Institute of Geological Sciences, Bern, Switzerland
Pages: 455-472
Published: 201206
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 25
Accession Number: 2012-092162
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 10 tables
N40°45'00" - N40°49'00", E40°30'00" - E40°37'00"
Secondary Affiliation: University of Silesia, POL, PolandMuseum d'Histoire Naturelle, CHE, SwitzerlandJagiellonian Centre for Experimental Therapeutics, POL, PolandRussian Academy of Sciences, Institute of Geology of Ore Deposits, Geochemistry, Mineralogy and Petrography, RUS, Russian Federation
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201248
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