In this study, we revealed the presence of hemocyanin proteins in the extracellular matrix of gastroliths deposited by the crayfish C. quadricarinatus. This identification results from the extensive mapping of the C. quadricarinatus gastrolith proteome and transcriptome we are currently performing, using the gastrolith as a simple model to study the involvement of proteins in crustacean skeletal construction. Initial identification of the proteins considered in this study was achieved by MS, as part of the proteomic mapping process, and was further supported by western blot analysis. The transcriptomic mapping yielded the partial sequences of nine hemocyanin transcripts, with the protein products of seven of them being found in the gastrolith matrix.