An experimental study of the role of ions at modulating the early stages of calcium carbonate formation

In the last decades numerous studies have shown that most calcifying organisms build their shells and skeletons via non-classical crystallization processes, including the formation of transient, metastable amorphous calcium carbonate (ACC) as a precursor phase. Although a significant progress has been achieved at understanding CaCO₃ growth via amorphous precursors, there are still aspects that remain unexplored. Knowledge of the role of different elements that are commonly co-precipitated with carbonates at modulating the early stages of calcium carbonate formation and the amorphous to crystalline transition is needed to constrain biomineralisation processes and to allow the understanding of how sensitive calcification is to past, current, and future environmental change. In order to address this issue, we investigated the incorporation of boron and magnesium into ACC precipitated under different pHs. This study evaluates the influence of B and Mg on the stability and water content of ACC and its formation mechanism. This information, together with an analysis of the B and Mg content of ACC formed at different pH conditions, provide insights into the factors controlling the chemical signatures and properties of the carbonate polymorphs formed via the ACC pathway.