A natural product that can play a role in jewellery making is nacre.It is a biological mineral, i.e. a material produced by a life form. Nacre, also known as mother-of-pearl, is formed by molluscs, which use it to build up their inner shell layer. It has a glittering, shimmering character and is therefore interesting for high-quality jewellery, musical instruments and also in the production of textiles. The animals that produce the nacre in the process of shell formation use its flashing and brightly coloured effects to ward off natural enemies. The gyre snails, the round-mouthed and turban snails as well as pearl oysters and other molluscs produce mother-of-pearl during the formation of their shells. Since the biomineral is a natural product, its appearance is always linked to the respective animal and its geographical location. Chemically, mother-of-pearl consists of a compound of calcium carbonate (95%) and other organic components. Mother-of-pearl is built up in layered structures that correspond in size to the wavelength of light. Therefore, the incident white light is also transmitted and reflected at each layer, which means a superposition. This superimposition is responsible for the changeable, iridescent colour play of the mother-of-pearl when the viewing angle is changed.
