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ABSTRACT: THE CHARACTERISATION OF CLAYS USING MICRO-REFLECTANCE SPECTROSCOPY
Coal Science Group
Energy Research Unit
University of Regina
Vibrational (infrared) spectroscopy can be used to characterise clays into the three major types, kaolinite, illite and montmorillonite. Transmission or DRIFTS techniques require the sample to be finely ground and mixed with KBr. The spectra are quantitative and the relative amounts of the clays present can be quickly and easily determined.
We have been developing the new technique of Micro-Reflectance Vibrational Spectroscopy to supplement these methods. Samples are either polished rocks or small particles mounted in resin and polished with isopropyl alcohol. They are initially characterized using conventional visible light microscopy. The spectra of positively identified portions of the sample, as small as 25 μm2, can be obtained by reflection from the polished surface. The conventional absorbance spectra are obtained from the reflection spectra by a Kramers-Kronig transform.
The success of vibrational spectral analyses in determining the composition of clay samples and in identifying the clays present in coal macerals and in carbonate and sandstone rocks will be discussed.