Calcium Carbonate (CaCO3) found in mussel shells, in calcite (a stable polymorph at room temperature), aragonite or vaterite form (the last two being metastable polymorphs), is biomineralized by energetically economic processes, which are not yet completely understood. Both calcite and aragonite would be nucleated from an amorphous phase of calcium carbonate (ACC), metaestable – highly soluble, this precursor phase provides material for the mechanism responsible for biomineralization. The older the shell, the harder it is to identify the ACC phase with Raman spectroscopy analysis.
