Hi, Syed. I think that I can help you on this question! But 

i do not have the answer you want: calcite, aragonite and vaterite are polymorphs of calcium carbonate. It is in fact the same chemical product, CaCO3, but crystallize. With different configurations, depending on the ambient conditions, and can suffer polymorphic transformations by theyselves, without the necessity of catalyst. The less crystalline product, vaterite, ihas low crystallinity and is the easiest formed. But, it can be easily transformed preferentially into calcite at ambient temperature and in aragonite above, say, 80C, if a small amount of water is present, allowing its dissolution and recrystallization. Some divalent salts sometimes interfeer in the mechanism, you will find a lot of literature on polymorphic change studies. The most stable is the most crystalline, calcite, a cubic shape crystal. Since aragonite is needle like crystal, is easy to identify the polimorphic phase on the electron microscopy.

well, 

i hope that this can help you.