In this study, the leaching kinetics of malachite [CuCO3.Cu(OH)(2)], an oxidized copper ore, was investigated in water saturated with ammonia gas. In the experiments, the ammonia concentration of the solution, the particle size of the ore, the temperature, the stirring speed, and the solid-to-liquid ratio were chosen as parameters. It was determined that the leaching rate of malachite increased with decreasing particle size and solid-to-liquid ratio and increasing reaction temperature, ammonia concentration, and stirring speed. The leaching kinetics was examined by statistical methods applied to the experimental data. It was found that the leaching rate fitted a pseudo-second-order kinetic model with an activation energy of 85.16 kJ(.)mol(-1).