The formation mechanism of ZrSiO4 in the cordierite-ZrO2 system was studied in the temperature range of 1250degrees to 1400degreesC by, X-ray diffraction analysis and discussed by analyzing experimental data using some reported reaction models. Nuclei growth models were found to describe the reaction well. and a satisfactory fit was obtained by applying the Avrami equation to estimate the reaction rate constant kappa. Different values of the time exponent in were obtained at different temperatures: 0.32 at 1250degreesC, 0.34 at 1300degreesC, 0.39 at 1350degreesC. and 0.49 at 1400degreesC. The results indicate that there is a progressive change in reaction mechanism.