Abstract: Experimental data are presented to show that the current auxilliary procedures adopted for identification of kaolinite in the presence of chlorite are not generally valid because the procedures often fail to give an explicit condition for distinguishing both the minerals.
As the result of an examination of numerous infrared spectra in the OH region of clay minerals, obtained by using Nippon Bunko DS-401G Grating Speetrophotometer, it turned out that the absorption band at 3698±2 cm−1 is effective for distinguishing kaolinite from other clay minerals without the use of any additional techniques. The absorption band seems to be less affected by variation of particle size and crystallinity than is the X-ray diffraction pattern. The band is detectable to a few weight percent of kaolinite in total amounts of clay minerals. Identification of kaolinite by its absorption spectrum in clay samples from sedimentary rocks was successful.