Aragonite formation through precipitation of calcium carbonate monohydrate

Formation of aragonite from amorphous, gelatinous CaCO 3 and CaCO 3 · H 2 O precipitated in the solution containing Mg 2+ ion was investigated. Amorphous CaCO 3 was converted to aragonite via CaCO 3 · H 2 O formation on drying in air. The stability of CaCO 3 · H 2 O in air depended on how long it has been immersed in the mother solution. Effect of Mg 2+ ion on the formation of aragonite was discussed on the basis of surface energy of a small particle.