THERMAL TRANSFORMATIONS OF VATERITE AND CALCITE

The polymorphic transition and the thermal decomposition of vaterite a re characterized. The effect of the morphology of the parent vaterite upon the polymorphic transition as well as upon the decomposition of p seudomorphous ex-vaterite, i.e. ''spherulitic'' calcite, is presented. It is shown for the first time that vaterite can be decomposed into c alcium oxide and carbon dioxide before being transformed into calcite. The nature of the evaluated kinetic parameters and derived mechanisti c interpretations are discussed.