Chief sources of mother of pearl are the pearl oyster, freshwater pearl mussels, and abalone. Nacre, also known as mother of pearl, is an iridescent organic-inorganic composite material produced by some mollusks as an inner shell layer and also is what makes up pearls. It is very strong, resilient, and iridescent. Nacre appears iridescent with different colors of light being reflected at different viewing angles. Lustrous and colorful, mother-of-pearl shell beads are commonly used in jewelry making and are a beautiful addition to most any craft creation. Lightweight enough for clustering and multiple layers!