The Pidgeon process, a silicothermic reduction of calcined dolomite under vacuum, is the dominant process to make magnesium metal. Experimental data from Morsi et al., were utilised for kinetics analysis of silicothermic reduction of calcined dolomite under argon atmosphere. A number of kinetic models were assessed to evaluate the rate-controlling step in the process. The results suggest that the reaction is controlled by the solid-state diffusion of reactants with the Jander and Ginstling-Brounshtein model providing the best representation of the process kinetics. Mass transfer effects of magnesium vapour from the surface to the bulk gas phase was also analysed. These results suggest that gas-film mass transfer is not the limiting step of the kinetics. Pore diffusion through briquettes is postulated to have some effect on the kinetics but solid-state diffusion is the major rate-limiting step.