Structural Differences Between Biogenic Amorphous Calcium Carbonate Phases Using X-ray Absorption Spectroscopy

We compare the organization of the first coordination shells around the calcium ion in biogenic ACC phases from three different sources. The results show that although the three biogenic samples have the same chemical composition, which is referred to collectively under the name “amorphous calcium carbonate”, they are structurally different from one another. These differences may be attributed to the diverse modes of formation of such biogenic materials and may account for their known variations in stability. Amorphous calcium carbonates (ACCs) that have the same chemical composition can still be structurally different. New X‐ray absorption spectroscopy analyses of three biogenic ACC phases (see Figure) show that their short range order is different. The differences in the three biogenic samples studied may be attributed to the diverse modes of formation and may account for their known variations in stability.