Raman spectroscopic study of various types of tourmalines

Both polarized and unpolarized Raman scattering studies of seven tourmalines from the Lucyen mines in Vietnam are presented. These tourmalines, according to their chemical compositions, can be classified into four groups: G1, liddicoatite; G2, elbaite; G3, uvite; and G4, feruvite. The Raman spectra were recorded in two spectral ranges, i.e. 150-1600 cm^-1 and 3000-4000 cm^-1. In the lower spectral range, which covers the metal ion-oxygen bond vibrations, all the observed A₁ and E modes are identified. In the higher spectral range, we investigated the OH stretching vibrations and showed that all the observed OH stretching modes have the A ₁ character. In both spectral ranges, we found that the same group classification of tourmalines can be applied, and the grouping characterizations are consistent with the chemical composition results.