The reactivities of olivine and serpentine towards mixture of chlorine in air, nitrogen and carbon monoxide were studied in non-isothermal conditions up to 1000 degrees C. The samples were also chlorinated in a horizontal reactor over 2 h between 500 degrees and 1000 degrees C, under oxidizing and reducing atmospheres. The chlorination products were examined by XRD and SEM. The iron-bearing compounds contained in the natural olivine and serpentine samples can be eliminated through chlorination or oxychlorination of these solids at temperatures lower than 900 degrees C. Carbochlorination of olivine and serpentine is incomplete even at 1000 degrees C for a reaction time of 2 h. Pure magnesium chloride can be recovered by cooling the gas phase at ca. 500 degrees C.