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Polytypic and polymorphic relations between sazhinite and isochemical alkali-REE layer silicates

Marcella Cadoni and Giovanni Ferraris
Polytypic and polymorphic relations between sazhinite and isochemical alkali-REE layer silicates
European Journal of Mineralogy (January 2011) 23 (1): 85-90

Abstract

An analysis of the crystal structures of natural and synthetic phases with ideal chemical formula A (sub 3) REE[Si (sub 6) O (sub 15) ].nH (sub 2) O (A=usually alkalis, n approximately 2) shows that they are either 2O (sub 2) polytypes or polymorphs of sazhinite, which represents the 1O (sub 1) polytype. The polytypic and polymorphic relations are essentially determined by the topology of the [Si (sub 6) O (sub 15) ] (super 6-) anion which is a corrugated sheet and varies according to the type of coalescence of the basic xonotlite-like module. The sheet can consist of: five- and eight-rings (5 (super 2) 8 (super 1) ring symbol); four-, six- and eight rings (4 (super 1) 6 (super 1) 8 (super 1) ); four-, five, six- and eight-rings (4 (super 1) 5 (super 1) 6 (super 2) 8 (super 2) ). The occurrence of weak reflections with h+k=2n+1 in the diffraction patterns of synthetic phases (space group Cmm2 and b=approximately 31 Aa) shows an isoriented presence of a minor sazhinite-type structure (space group Pmm2 and b= approximately 15.5 Aa).


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 23
Serial Issue: 1
Title: Polytypic and polymorphic relations between sazhinite and isochemical alkali-REE layer silicates
Affiliation: Universita di Torino, Dipartimento di Scienze Mineralogiche e Petrologiche, Via Valperga Caluso 35, 10125 Torino, Italy Nanostructured Interfaces and Surfaces (NIS) Centre of Excellence, University of Torino, Turin, Italy
Pages: 85-90
Published: 201101
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 21
Accession Number: 2011-026560
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
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: 201115
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