Mother-of-pearl is an organic substance produced by certain molluscs, notably oysters and pearl mussels. It is found inside their shell and is mostly made up of aragonite, a type of calcium carbonate. Mother-of-pearl is known for its beautiful iridescence and shimmering reflections, which give it great aesthetic value. It has been used for centuries in the manufacture of jewelry and decorative objects. The production of nacre is a slow process, as molluscs secrete it layer by layer over time. Mother of pearl is also considered a symbol of purity, protection and luck in some cultures.