Three kaolinitic materials from different sources have been studied by means of scanning electron micrography, X-ray diffraction, infrared analysis and thermal analysis. Observation were made on the raw samples as well as on samples fired at 300^oC, 500^oC, 700^oC, 900^oC, 1100^oC and 1250^oC. The scanning electron micrographs of the raw samples reveal that the Magpet clay specimen consists of hexagonal particles, while both Lamba and Talakag clay specimens consist mainly of spherical particles. The former has finer grain size. The unheated samples exhibited an absorption band in the OH region registering from 3700 cm^-1 to 3630 cm^-1. On the other hand, the sample heated at 300^oC and 500^oC show a total discharge of interlayer and structural water, respectively. X-my diffraction pattern showed the heated specimen decompose at 500^oC and form into a metakaolin at a temperature of 700 - 900^oC, and is further converted to a poorly crystallized mullite at 1100^oC.