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Compositional control of plane group symmetry in tourmalines; an experimental and computer simulated TEM, crystallographic image processing and Moessbauer spectroscopy study

Embaie A. Ferrow, L. Reine Wallenberg and Henrik Skogby
Compositional control of plane group symmetry in tourmalines; an experimental and computer simulated TEM, crystallographic image processing and Moessbauer spectroscopy study
European Journal of Mineralogy (June 1993) 5 (3): 479-492

Abstract

Tourmalines with different compositions show different plane group symmetries in experimental HRTEM when projected along the c axis. Fe-poor elbaite shows p31m symmetry, while Fe-bearing elbaite shows p3ml symmetry. Rubellite shows p6 symmetry, while Fe-Mg-Al- bearing tourmaline shows a 'pseudo' p6 type of symmetry. Symmetries p3ml and p6 are not compatible with the space group R3m assigned to tourmaline from XRD structure determinations. The perturbations of symmetry depend on the magnitude of the scattering amplitude of the atoms occupying the 3a and 9b sites. Computer simulations of elbaite, schorl and dravite show different projected potentials for images down the c axis. In Fe-poor elbaite regions with high mean concentration of light or heavy elements a few unit cells apart are common, giving a marked difference in the distribution contrast in the HRTEM image. Experimental HRTEM, computer simulation and Mossbauer spectroscopy all indicate that in tourmaline the composition controls symmetry.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 5
Serial Issue: 3
Title: Compositional control of plane group symmetry in tourmalines; an experimental and computer simulated TEM, crystallographic image processing and Moessbauer spectroscopy study
Affiliation: Lund University, Department of Mineralogy and Petrology, Lund, Sweden
Pages: 479-492
Published: 199306
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 21
Accession Number: 1993-017375
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Secondary Affiliation: National Center for HREM, SWE, SwedenUppsala University, 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: 1993
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