Thermal activation of kaolinite plays a critical role in determining its suitability for industrial and environmental applications, particularly for the production of reactive metakaolin. In this study, a quantitative and mechanistically informed evaluation of the amorphization and dehydroxylation behaviour of Ikere-Ekiti kaolin was conducted following calcination at temperatures between 550 and 850 °C for residence times of 15- and 120-min. Fourier-transform infrared (FTIR) spectroscopy was employed to monitor structural evolution, with emphasis on hydroxyl group removal and collapse of the kaolinite lattice. The persistence of O–H stretching bands at 3697 and 3622 cm⁻¹ after calcination at 550 °C for 15 min indicates incomplete metakaolinization, whereas their disappearance at higher temperatures and longer durations confirms extensive dehydroxylation. Quantitative analysis based on spectral deconvolution and normalization reveals that amorphization is strongly dependent on both temperature and time, reaching a maximum near 650 °C after 120 min. Calcination above 750 °C results in a slight decrease in structural disorder, suggesting the onset of reorganization toward spinel-type intermediates. A schematic transformation pathway and a pseudo-Arrhenius interpretation of dehydroxylation kinetics are proposed. These results identify an optimal activation window for kaolinite and provide general insight into thermally driven transformations of layered aluminosilicates.