Physics and Chemistry of Minerals

, Volume 25, Issue 2, pp 142–151 | Cite as

Raman spectra of silicate garnets

  • B. A. Kolesov
  • C. A. Geiger


The single-crystal polarized Raman spectra of four natural silicate garnets with compositions close to end-members almandine, grossular, andradite, and uvarovite, and two synthetic end-members spessartine and pyrope, were measured, along with the powder spectra of synthetic pyrope-grossular and almandine-spessartine solid solutions. Mode assignments were made based on a comparison of the different end-member garnet spectra and, in the case of pyrope, based on measurements made on additional crystals synthesized with 26Mg. A general order of mode frequencies, i.e. R(SiO4)>T(metal cation)>T(SiO4), is observed, which should also hold for most orthosilicates. The main factors controlling the changes in mode frequencies as a function of composition are intracrystalline pressure (i.e. oxygen-oxygen repulsion) for the internal SiO4-vibrational modes and kinematic coupling of vibrations for the external modes. Low frequency vibrations of the X-site cations reflect their weak bonding and dynamic disorder in the large dodecahedral site, especially in the case of pyrope. Two mode behavior is observed for X-site cation vibrations along the pyrope-grossular binary, but not along the almandine-spessartine join.


Mode Frequency Mode Behavior Orthosilicate External Mode Almandine 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • B. A. Kolesov
    • 1
  • C. A. Geiger
    • 2
  1. 1.Institute of Inorganic Chemistry, Lavrentiev prosp. 3, Novosibirsk 630090, RussiaRU
  2. 2.Mineralogisch-Petrographisches Institut, Universität Kiel, Olshausenstr. 40, D-24098 Kiel, Germany Fax: +49 04 31 8 80-44 57; e-mail: NMP4b@rz.uni-kiel.deDE

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