Kaolin wastes from the Capim and Jari regions (Brazil) were used to produce sodalite under the same conditions used in the Bayer process, in order to control its formation when necessary. Of the two kaolin source materials, the kaolinite from the Jari region was more reactive in the synthesis of sodalite, which is attributed to the low degree of structural order of this clay mineral which increased its reactivity. At a temperature of 150°C and with a Na/Al ratio of 2, although the kaolinite did not react completely, sodalitewas the primary reaction product. An increase in the temperature to 200°C provoked the complete reaction of the kaolinite only for the products in which carbonate and sulfate were used. With a Na/Al ratio >2 and for both of the temperatures, the kaolinite reacted completely to form sodalite.