The structure of the kaolinite minerals - A FT-Raman study

The Fourier transform Raman spectra of the kaolinite minerals have been measured in the 50-3800 cm(-1) region using near infrared spectroscopy. Kaolinites are characterized by remarkably intense bands in the 120-145 cm(-1) region. These bands, attributed to the O-Si-O and O-Al-O symmetric bending modes, are both polymorph and orientation dependent. The 200-1200 cm(-1) spectral range is a finger-print region for clay minerals and each kaolinite clay has its own characteristic spectrum. The structure of clays is fundamentally determined by the position of hydroxyl groups. Fourier-transform Raman spectroscopy readily enables the hydroxyl stretching region to be examined allowing identification of the component bands. The advantages of FT-Raman spectroscopy are shown to enhance the study of the kaolinite structure.