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Crystal chemistry and defect structure of ekmanite : New data from transmission electron microscopy and Mossbauer spectroscopy

Ferrow, Embaie A. LU ; Wallenberg, LR LU and Holtstam, Dan (1999) In European Journal of Mineralogy 11(2). p.299-308
Abstract
Ekmanite is a member of the 2:1 type modulated layer silicates such as ganophyllite and bannisterite. Its chemical composition can be represented by K(M20)[Si32O76](OH)16 (M = Fe2+, Mg2+, Mn2+) where three of eight Si-tetrahedra are 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 of possibly high Mg/(Mn+Fe) ratio, this configuration is interrupted by the absence of inverted tetrahedra. Ekmanite typically contains a multitude of defects; twinning and both regular and irregular stacking arrangements are the most common ones. Ekmanite is... (More)
Ekmanite is a member of the 2:1 type modulated layer silicates such as ganophyllite and bannisterite. Its chemical composition can be represented by K(M20)[Si32O76](OH)16 (M = Fe2+, Mg2+, Mn2+) where three of eight Si-tetrahedra are 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 of possibly high Mg/(Mn+Fe) ratio, this configuration is interrupted by the absence of inverted tetrahedra. Ekmanite typically contains a multitude of defects; twinning and both regular and irregular stacking arrangements are the most common ones. Ekmanite is sensitive to oxidation and an unidentified phase, chemically related to it, is always found lining its grain boundaries. This texture results in intergrown rods defining polygons where the central parts do not contain ekmanite. The Mossbauer spectrum consists of Fe2+ and Fe3+ absorption doublets with the Fe2+ absorption composed of two Gaussian line pairs and the Fe3+ absorption of a single but broad line pair. (Less)
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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
ekmanite, HRTEM, Mossbauer spectroscopy, modulated structure, defects, image processing
in
European Journal of Mineralogy
volume
11
issue
2
pages
10 pages
publisher
Copernicus GmbH
external identifiers
  • scopus:0033026073
ISSN
0935-1221
language
English
LU publication?
yes
id
08bd1ee8-3500-4d80-844c-a18c5cede56c
date added to LUP
2023-10-31 16:16:05
date last changed
2023-11-02 14:04:14
@article{08bd1ee8-3500-4d80-844c-a18c5cede56c,
  abstract     = {{Ekmanite is a member of the 2:1 type modulated layer silicates such as ganophyllite and bannisterite. Its chemical composition can be represented by K(M20)[Si32O76](OH)16 (M = Fe2+, Mg2+, Mn2+) where three of eight Si-tetrahedra are 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 of possibly high Mg/(Mn+Fe) ratio, this configuration is interrupted by the absence of inverted tetrahedra. Ekmanite typically contains a multitude of defects; twinning and both regular and irregular stacking arrangements are the most common ones. Ekmanite is sensitive to oxidation and an unidentified phase, chemically related to it, is always found lining its grain boundaries. This texture results in intergrown rods defining polygons where the central parts do not contain ekmanite. The Mossbauer spectrum consists of Fe2+ and Fe3+ absorption doublets with the Fe2+ absorption composed of two Gaussian line pairs and the Fe3+ absorption of a single but broad line pair.}},
  author       = {{Ferrow, Embaie A. and Wallenberg, LR and Holtstam, Dan}},
  issn         = {{0935-1221}},
  keywords     = {{ekmanite; HRTEM; Mossbauer spectroscopy; modulated structure; defects; image processing}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{2}},
  pages        = {{299--308}},
  publisher    = {{Copernicus GmbH}},
  series       = {{European Journal of Mineralogy}},
  title        = {{Crystal chemistry and defect structure of ekmanite : New data from transmission electron microscopy and Mossbauer spectroscopy}},
  volume       = {{11}},
  year         = {{1999}},
}