Nacre, also known as mother of pearl is a valuable material, made from the inner layer of the shell of certain mollusks, especially the pinctada maxima (white iridescent pearly color) and the cuminingi pinctada margaritifera (black/gray color). Nacre is composed of hexagonal platelets of aragonite arranged in a continuous parallel lamina. These layers are are separated by sheets of organic matrix composed of biopolymers. The mixture of brittle platelets and the thin layer of elastic biopolymers makes the material strong and resilient. Pearl and nacre differ only for the arrangement of the crystals which are concentric in the pearl and in a parallel way in the nacre.