Abstract
Polarized Raman (Ra) and IR reflection spectra from single crystals of olivine, forsterite, monticellite and tephroite have been measured and assigned. Comparing the different spectra including those of other substances of the same structure, it could be shown, that the four stretching vibrations of the SiO4 tetrahedra are the only vibrations which may be interpreted as independent group vibrations. Cation typical vibrations are more or less strongly coupled to the deformation vibrations of the SiO4 tetrahedra.