In order to better understand the thermodynamic stability and structure of gastrolith mineral in relationship to its biological formation history and purpose, in this study we performed
spatially-resolved analysis on whole pre-molt gastrolith slices or cross-sections. To obtain a complete chemical, structural and morphological description of the gastrolith at different length scales, Raman spectroscopy and synchrotron small-and wide angle X-ray scattering (SAXS/WAXS) were combined with light microscopy imaging, high-resolution scanning electron microscopy (SEM) and EDS analysis. Results show that the structure as well as the content of inorganic phosphate, chitin, protein and citrate or PEP show layer-to-layer variations. Such a distribution indicates that the remarkable stability of the ACC is not governed by only
one of these compounds, but that depending on the specific layer investigated, different stabilizing agents are involved.