X-ray Studies on the Transformation of Aragonite to Calcite in the Marine Molluscan Shell

X-ray studies are made on marine molluscan shell which has essentially aragonite structure. The transformation temperature of aragonite to calcite is found to start at 300°C. X-ray reflections of aragonite were found to be broader whereas after the transformation the calcite reflections were sharper. From the study of half width at peak maximum of aragonite and calcite reflection it is concluded that transformation induced annealing and/or recrystallizalion might be occurring when the crystal structure is changing from aragonite to calcite