FT-Raman spectroscopy on several di- and tri- octaedral T-O-T phyllosilicates

Pure phases of several di-octahedral (muscovite, Ca and Na-montmorillonites) and tri-octahedral (phlogopite, vermiculite and hectorite) T–O–T phyllosilicates have been studied by FT-Raman spectroscopy to determine whether there are characteristic vibrations for each family of minerals. The samples were first characterized by X-ray powder diffraction and then underwent Raman spectroscopy, spectral region 95 –1200 cm–1. The results revealed a band produced by the symmetric stretching modes of the SiO4 tetrahedra occurring near 680 cm–1 for the tri-octahedral phyllosilicates, and an equivalent band for di-octahedral phyllosilicates occurring near 700 cm–1. Another diagnostic pattern allowing rapid identification of the minerals studied is created by bands corresponding to the antisymmetric stretching modes of the SiO4 tetrahedra and to the vibrations of the O–H–O groups.