Mother of pearl is created by means of glands, which leaves a mother of pearl secretion. The secretion is left in many thin layers on top of each other. Each layer of mother of pearl is “glued” together with a layer of protein. The layers are so thin that it takes a thousand layers to reach a total thickness of 0,5 mm. Depending on the water temperature and the mussel’s nature and physics it can make 2-7 layers a day. When the light is reflected through these layers, the pearl gets a rainbow luster.