Physics and Chemistry of Minerals

, Volume 29, Issue 1, pp 78–86

Characterization of beryl (aquamarine variety) by Mössbauer spectroscopy

Authors

  • R. R. Viana
    • Departamento de Geologia, Universidade Federal de Ouro Preto, Ouro Preto, Brazil
  • G. M. da Costa
    • Departamento de Química, Universidade Federal de Ouro Preto, Ouro Preto, Brazil Tel.: +00-55-31-3359-1708; 00-55-31-99613810 Fax: +00-55-31-3559-1660 e-mail: magela@iceb.ufop.br
  • E. De Grave
    • Department of Subatomic and Radiation Physics, University of Gent, Gent, Belgium
  • H. Jordt-Evangelista
    • Departamento de Geologia, Universidade Federal de Ouro Preto, Ouro Preto, Brazil
  • W. B. Stern
    • Mineralogisch-Petrographisches Institut, University of Basel, Basel, Switzerland
ORIGINAL PAPER

DOI: 10.1007/s002690100210

Cite this article as:
Viana, R., da Costa, G., De Grave, E. et al. Phys Chem Min (2002) 29: 78. doi:10.1007/s002690100210

Abstract

 The Mössbauer spectra of several blue beryls have been obtained in the temperature range of 4.2–500 K. A common feature observed in all room-temperature spectra is the presence of an asymmetric Fe2+ doublet (ΔEQ ∼ 2.7 mm s−1, δ ∼ 1.1 mm s−1), with a very broad low-velocity peak. This asymmetry seems to be related to a relaxation process involving ferrous ions and water molecules in the structural channels, as suggested by Price et al. (1976). Surprisingly, the spectrum at 500 K also shows a broad, but symmetrical, doublet, with a clear splitting of the lines indicating the presence of at least two Fe2+ components. The room-temperature spectrum obtained after the 500 K run shows the same features as prior to the heating. At 4.2 K the spectrum of a deep blue beryl was well fitted with four symmetrical doublets, one of which could be related to Fe2+ in the structural channels. Ferrous ion was also found to occupy the octahedral and tetrahedral sites, whereas ferric ion is most probably located in the octahedral site. A meaningful fit of the room-temperature spectrum, as well as an explanation for the temperature dependence of the Mössbauer spectra, are discussed. Finally, it is believed that the color in beryl will be dictated by the relative proportions of Fe3+ in the octahedral sites and of Fe2+ in the channels.

Keywords BerylMössbauer spectroscopy

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© Springer-Verlag Berlin Heidelberg 2002