The thermal decomposition of the kaolinite: N-methylformamide intercalate [Al2Si2O5(OH)4·HCONHCH3] has been studied by differential scanning calorimetry (DSC). The decomposition starts at 355 K, finishes at 450 K and follows Avrami-Erofeev kinetics for α = 0.04–0.96. ΔH for the loss of organic is 19 ± 2 kJ mol−1; the activation energy for the reaction is 30 ± 3 kJ mol−1.