In recent years, it has been observed that the formation of stable crystalline polymorphs of CaCO3 is preceded by the precipitation of an amorphous phase -Amorphous Calcium Carbonate (ACC)-, which contains structural water. ACC is found in the first steps of formation of many organisms (see for instance the prototypical example of sea urchin). ACC usually contains a small weight fraction of some organic and inorganic additives, whose role is not yet fully understood. Laboratory studies have shown that Mg2+ plays a role as stabilizer of the amorphous structure, preventing its crystallization. In a recent experiment at LAGRANGE we proved false the hypothesis that Mg2+ was acting as a stabilizer of the amorphous structure through the stiffening of H-bonding, as it had been suggested by molecular dynamics simulations. Here, we aim to explore the role of organics as modifiers of the water H-bond network in ACC.