The near-infrared combination band frequencies of dioctahedral smectites, micas, and illites

Abstract

The highest frequency near-infrared (NIR) combination bands for specimens of four species of mica-montmorillonite-beidellite, illite, chlorite, and kaolinite-were correlated with respect to Al2O3 content. A direct linear correlation was found between the combination band positions and the Al2O3 contents of the montmorillonite-beidellite series, which may be given as: ν̄ cm-1 = (5.38 ± 0.04) (% Al2O3) + (4412.8 ± 0.9). A similar linear correlation for muscovite is: ν̄ cm-1 = (6.10 ± 0.25) (% Al2O3) + (4434.1 ± 8.3). Possible NIR band interferences are shown for different mineral mixtures, along with the correlation of different illites with muscovite. No combination bands were found in the frequency region 4425 cm-1 to 4625 cm-1 for specimens in which the Al2O3 content was only in the tetrahedral layer sites. © 1993, The Clay Minerals Society.