Smectites including the iron-bearing smectites have proved difficult to measure using the techniques of Raman spectroscopy. The use of Fourier transform (FT)-Raman spectrometers using indium-gallium-arsenide detectors has enabled the spectra of a selection of high iron-bearing smectites and nontronites to be measured. Low-intensity hydroxyl stretching Raman bands were found at 3436 and 3355cm -1 and are attributed to the Fe-FeOH unit. Low-frequency bands were observed at around 201, 163, 128, and 90cm -1. The 90cm -1 band is ascribed to the stretching vibration of the hydrated cation. Bands observed at around 780 and 880cm -1 are ascribed to the hydroxyl deformation modes of the Fe-FeOH and Fe-AlOH. Index Headings: Ferruginous smectite; FT-Raman spectroscopy; Montmorillonite; Nontronite; Smectite.
Ray L. Frost and J. Theo Kloprogge, "Raman Spectroscopy of Nontronites," Appl. Spectrosc. 54, 402-405 (2000)