Accordingly, the amorphous mineral attaches on this matrix as nanometer-sized spheres
(Travis, 1963). In this process, both the chitin matrix and the mineral particles are secreted by the epidermal cells of the gastrolith disk. As the gastrolith matures, new mineral is deposited on the external layer, while the earlier deposited mineral densifies into macroscopic columnar structures, directed parallel to the growth direction. In time, the composite of the lamellar chitin and the mineral forms an ordered structure of concentric layers (Travis,1963), which is finally resorbed through collapse of the tissue into the crayfish stomach during ecdysis (Shechter et al., 2008a).