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 3355 cm−1 and are attributed to the Fe–FeOH unit. Low-frequency bands were observed at around 201, 163, 128, and 90 cm−1. The 90 cm−1 band is ascribed to the stretching vibration of the hydrated cation. Bands observed at around 780 and 880 cm−1 are ascribed to the hydroxyl deformation modes of the Fe–FeOH and Fe–AlOH.
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