Visible and near-infrared spectroscopic comparison of five phyllosilicate mineral samples

Portable visible and near-infrared (vis/NIR) spectroscopy was used to characterize and differentiate the five phyllosilicate minerals and relate the bands to the mineral structure. The feature band at 2160-2170nm (4600-4630cm^-1) has been assigned to the high presence of Al-OH and is described as typical of dioctahedral phyllosilicate with OH groups coordinated around Al, and the feature occurred near 2322nm is considered to be due to a combination of the OH stretch with the MgOH deformation mode, which is a typical of trioctahedral phyllosilicates. The presence of the bands 1400 and 1900nm in vis/NIR spectrum indicated that some water is present in this sample. The absence of a 1900nm band but the presence of a 1400nm band indicates that only OH is present. Moreover, the significant differences between these five minerals were observed by the portable vis/NIR spectroscopy. The results show a potential for the application of vis/NIR spectroscopy in the identification and quantification of these minerals in the field. Further, such analysis can also provide important constraints on the nature of putative global and local-scale mineralogical transitions on Mars.