Upon calcinations at 600 C for 3 h, the XRD patterns exhibit the expected significant change in comparison to the pattern of untreated kaolin, which was characterized by the disappearance of the diffraction peaks of kaolin, accompanied by the appearance of amorphous aluminosilicate. Metakaolin is of amorphous material and the highest diffraction peaks correspond to the presence of quartz (SiO2), which is the crystalline phase, in metakaolin (Fig. 1a).