Cultured pearl is calcium carbonate and a fibrous protein called conchiolin. As the nacre builds up in layers of minute aragonite tablets, it fills the growing pearl sac and eventually forms a pearl. Natural pearls are formed by nature, more or less by chance. On the other hand, cultured pearls are human creations formed by inserting a tissue graft from a donor oyster, upon which a pearl sac forms, and the inner side precipitates calcium carbonate, in the form of nacre or "mother-of-pearl". The most popular and effective method for creating cultured pearls are made from the shells of freshwater river mussels
The Pearl and the Wave "The Pearl and the Wave" as "the most perfect painting of the nude" in the 19th century. Cox identified some features in the painting which he described as "grace of attitude", the well-rounded but slim body of a young woman, the visible dimple in the shoulder, the "savoring of subtle line", the "loveliness of the color", the "solid yet mysterious modelling", and the "perfection of delicate surface". Cox believed these features make this painting what he calls "a pure masterpiece". Art historian Bailey Van Hook identified "The Pearl and the Wave" as one of the examples of nude paintings where