Hostname: page-component-848d4c4894-x24gv Total loading time: 0 Render date: 2024-05-29T01:32:08.029Z Has data issue: false hasContentIssue false
  • English
  • Français

Coexistence of Two Polytypic Groups in Cronstedtite From Lostwithiel, England

Published online by Cambridge University Press:  01 January 2024

Toshihiro Kogure ,
Jiří Hybler  and
Hideto Yoshida
Toshihiro Kogure*
Affiliation:
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
Jiří Hybler
Affiliation:
Institute of Physics, Science Academy of the Czech Republic, Na Slovance 2, CZ-18221, Praha 8, Czech Republic
Hideto Yoshida
Affiliation:
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
*
*E-mail address of corresponding author: kogure@eps.s.u-tokyo.ac.jp
Get access Rights & Permissions [Opens in a new window]

Abstract

Cronstedtite from Lostwithiel, Cornwall, England, in which two polytypic groups (A and C) are present within the same crystal, has been investigated using various techniques to reveal the distribution of the two groups and the relationship between polytypic structure and chemical composition. X-ray precession photographs from cleaved fragments of pyramidal crystals revealed the variable proportions of the two groups from the top to the base. Near the top, the crystal consists entirely of group C, with 1T as the dominant polytype. Near the base, both groups A and C are present. Back-scattered electron images from cross-sections parallel to the pyramidal axis showed mosaic contrast near the base, suggesting that two compositionally-different domains of several tens of microns in size are present, whereas the contrast was uniform near the top. Electron microprobe chemical analysis indicated the compositions (Fe2.312+Fe0.693+)(Si1.31Fe0.693+)O5(OH)4 and (Fe2.162+Fe0.843+)(Si1.16Fe0.843+)O5(OH)4. Electron back-scattered patterns (EBSPs) confirmed that the domain with Si-rich composition belongs to group C and that with Si-poor composition to group A. This is the first evidence that specific chemical compositions are related to the polytypic structures in cronstedtite. Transmission electron microscopy revealed that intergrowth of groups A and C at the monolayer level is also present as stacking disorder in both domains near the base, whereas such intergrowth was not observed in the region near the top.

Keywords

CronstedtiteEBSPIntergrowth1:1 PhyllosilicatesPolytypism
Type
Research Article
Information
Clays and Clay Minerals , Volume 50 , Issue 4 , August 2002 , pp. 504 - 513
Copyright
Copyright © 2002, The Clay Minerals Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bailey, S.W., (1969) Polytypism of trioctahedral 1:1 layer silicates Clays and Clay Minerals 17 355–371 10.1346/CCMN.1969.0170605.CrossRefGoogle Scholar
Bailey, S.W. and Bailey, S.W., (1988) Polytypism of 1:1 layer silicates Hydrous Phyllosilicates (Exclusive of Micas) Washington, D.C. Mineralogical Society of America 9–27 10.1515/9781501508998-007 Reviews in Mineralogy, 19. .CrossRefGoogle Scholar
Bailey, S.W. and Bailey, S.W., (1988) Structure and compositions of other trioctahedral 1: 1 phyllosilicates Hydrous Phyllosilicates (Exclusive of Micas) Washington, D.C. Mineralogical Society of America 169–188 10.1515/9781501508998-011 Reviews in Mineralogy, 19. .CrossRefGoogle Scholar
Dingley, D.J. and Randle, V., (1992) Microtexture determination by electron back-scatter diffraction Journal of Material Science 27 4545–4566 10.1007/BF01165988.CrossRefGoogle Scholar
Dornberger-Schiff, K. and Ďurovič, S., (1975) OD interpretation of kaolinite-type structures — I: Symmetry of kaolinite packets and their stacking possibilities Clays and Clay Minerals 23 219–229 10.1346/CCMN.1975.0230310.CrossRefGoogle Scholar
Dornberger-Schiff, K. and Ďurovič, S., (1975) OD interpretation of kaolinite-type structures — II: The regular polytypes (MDO polytypes) and their derivation Clays and Clay Minerals 23 231–246 10.1346/CCMN.1975.0230311.CrossRefGoogle Scholar
Ďurovič, S., (1997) Cronstedtite-1M and coexistence of 1M and 3T polytypes Ceramics-Silikáty 41 98 104.Google Scholar
Frondel, C., (1962) Polytypism in cronstedtite American Mineralogist 47 781 783.Google Scholar
Goehner, R.P. and Michael, J.R., (1996) Phase identification in a scanning electron microscope using backscattered electron Kikuchi patterns Journal of Research of the National Institute of Standards and Technology 101 301–308 10.6028/jres.101.031.CrossRefGoogle Scholar
Hybler, J. Petříček, V. Ďurovič, S. and Smrčok, L., (2000) Refinement of the crystal structure of the cronstedtite-1T Clays and Clay Minerals 48 331–338 10.1346/CCMN.2000.0480304.CrossRefGoogle Scholar
Hybler, J., Petříček, V., Fábry, J. and Ďurovič, S. (2002) Refinement of the crystal structure of cronstedtite-2H 2. Clays and Clay Minerals, in press.Google Scholar
Kogure, T. (2002) Identification of polytypic groups in hydrous phyllosilicates using Electron Back-Scattering Patterns (EBSPs). American Mineralogist, in press.CrossRefGoogle Scholar
Kogure, T. Hybler, J. and Ďurovič, S., (2001) A HRTEM study of cronstedtite: Determination of polytypes and layer polarity in trioctahedral 1:1 phyllosilicates Clays and Clay Minerals 49 310–317 10.1346/CCMN.2001.0490405.CrossRefGoogle Scholar
Smrčok, L. Ďurovič, S. Petříček, V. and Weiss, Z., (1994) Refinement of the crystal structure of cronstedtite-3.T Clays and Clay Minerals 42 544–551 10.1346/CCMN.1994.0420505.CrossRefGoogle Scholar
Steadman, R., (1964) The structures of trioctahedral kaolin-type silicates Acta Crystallographica 17 924–927 10.1107/S0365110X64002390.CrossRefGoogle Scholar
Steadman, R. and Nuttall, P.M., (1963) Polymorphism in cronstedtite Acta Crystallographica 16 1–8 10.1107/S0365110X63000013.CrossRefGoogle Scholar
Steadmann, R. and Nuttall, P.M., (1964) Further polymorphism in cronstedtite Acta Crystallographica 17 404–406 10.1107/S0365110X64000913.CrossRefGoogle Scholar