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Characterization of beryl (aquamarine variety) by Mössbauer spectroscopy

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Abstract
The Mossbauer 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 (DeltaE(Q) similar to 2.7 mm s(-1), delta similar to 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 Mossbauer 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
Mossbauer spectroscopy, beryl, CORDIERITE, SPECTRA, BLUE

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Chicago
Viana, RR, GM da Costa, Eddy De Grave, H Jordt-Evangelista, and WB Stern. 2002. “Characterization of Beryl (aquamarine Variety) by Mössbauer Spectroscopy.” Physics and Chemistry of Minerals 29 (1): 78–86.
APA
Viana, R., da Costa, G., De Grave, E., Jordt-Evangelista, H., & Stern, W. (2002). Characterization of beryl (aquamarine variety) by Mössbauer spectroscopy. PHYSICS AND CHEMISTRY OF MINERALS, 29(1), 78–86.
Vancouver
1.
Viana R, da Costa G, De Grave E, Jordt-Evangelista H, Stern W. Characterization of beryl (aquamarine variety) by Mössbauer spectroscopy. PHYSICS AND CHEMISTRY OF MINERALS. 2002;29(1):78–86.
MLA
Viana, RR, GM da Costa, Eddy De Grave, et al. “Characterization of Beryl (aquamarine Variety) by Mössbauer Spectroscopy.” PHYSICS AND CHEMISTRY OF MINERALS 29.1 (2002): 78–86. Print.
@article{166491,
  abstract     = {The Mossbauer 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 (DeltaE(Q) similar to 2.7 mm s(-1), delta similar to 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 Mossbauer 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.},
  author       = {Viana, RR and da Costa, GM and De Grave, Eddy and Jordt-Evangelista, H and Stern, WB},
  issn         = {0342-1791},
  journal      = {PHYSICS AND CHEMISTRY OF MINERALS},
  keyword      = {Mossbauer spectroscopy,beryl,CORDIERITE,SPECTRA,BLUE},
  language     = {eng},
  number       = {1},
  pages        = {78--86},
  title        = {Characterization of beryl (aquamarine variety) by M{\"o}ssbauer spectroscopy},
  url          = {http://dx.doi.org/10.1007/s002690100210},
  volume       = {29},
  year         = {2002},
}

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