Displacement reactions in gypsum and in anhydrite

Displacement reactions between calcium sulfates (gypsum and anhydrite) and aqueous solutions of Ba⁻, Sr⁻ and Pb-salts were investigated by means of TG, DSC,microscopy and x-ray. The reactions can be followed directly by microscopy when cleavage plates of gypsum crystals are used. The first steps of crystallization are in some cases of a topotactical nature. The results presented in this paper deal mainly with the formation of barite, celestite and anglesite by displacement reactions at different temperatures.