Mother Of Pearl & Shell Mosaic: The pearly internal layer of certain mollusk shells, used to make decorative sheets. It is an iridescent layer of material that forms the shell lining of many mollusks. Pearl oysters and abalone are both sources of this substance, which is widely used as an inlay in jewelry, furniture, and musical instruments. Mother of pearl comes in several natural colors, but is often bleached and dyed for decorative use. The dye retains the shimmering layers which make the material so sought after. Mother of pearl is a tough and resilient material, but it is relatively soft and easily scratched.