Raman spectroscopy of clay minerals.

Raman spectroscopy of clay minerals has received less attention than infrared (IR)spectroscopy in the past, generally due to the weakness of the Raman scattered signal, laser-induced photo-degradation of the sample, and the occurrence of fluorescence, which often swamps the signal. Progress in instrumentation, however, has improved the quality of the Raman spectra and now enables the investigation of clay minerals in more detail. This chapter reports on comprehensive Raman spectroscopic studies of selected representatives of the main clay mineral groups following literature published mainly during the last 20 years. The emphasis is on the interpretation of the individual Raman vibrational modes, based not only on the comparison with other minerals, but also on the calculations and molecular modelling, providing theoretical values of the individual vibrational modes.