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Crystal chemistry and defect structure of ekmanite; new data from transmission electron microscopy and Moessbauer spectroscopy

Embaie A. Ferrow, L. Reine Wallenberg and Dan Holtstam
Crystal chemistry and defect structure of ekmanite; new data from transmission electron microscopy and Moessbauer spectroscopy
European Journal of Mineralogy (April 1999) 11 (2): 299-308

Abstract

The 2:1 type modulated layer silicate ekmanite, K(M (sub 20) )[Si (sub 32) O (sub 76) ](OH) (sub 16) where M = Fe (super 2+) , Mg (super 2+) , Mn (super 2+) , has three of the eight Si tetrahedra inverted across the interlayer sharing an apical oxygen with similarly inverted tetrahedra from the adjacent layers. The arrangement of the regular, D, and inverted, R, tetrahedra has the configuration 4D2R1D1R4D... along the b axis; in local regions possibly of high Mg/(Mg +Fe) ratio, this configuration is interrupted by the absence of inverted tetrahedra. Eckmanite typically has a multitude of defects, including twinning and irregular stacking arrangements. It is sensitive to oxidation and an unidentified chemically-related phase is always found lining its grain boundaries. This texture results in intergrown rods defining polygons where the central parts do not contain eckmanite. The Moessbauer spectrum consists of Fe (super 2+) and Fe (super 3+) absorption doublets with the Fe (super 2+) absorption composed of two Gaussian pair lines and the Fe (super 3+) absorption of a single broad line pair.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 11
Serial Issue: 2
Title: Crystal chemistry and defect structure of ekmanite; new data from transmission electron microscopy and Moessbauer spectroscopy
Affiliation: Lund University, Department of Mineralogy & Petrology, Lund, Sweden
Pages: 299-308
Published: 199904
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 16
Accession Number: 1999-035209
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: Center for Chemistry and Chemical Engineering, SWE, SwedenSwedish Museum of Natural History, SWE, Sweden
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199912
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