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
Parable of the Pearl story. However, those who do not believe in the kingdom of heaven enough to stake their whole future on it are unworthy of the kingdom. This interpretation of the parable is the inspiration for a number of hymns, including the anonymous Swedish hymn "Den Kostliga Pärlan" ("O That Pearl of Great Price!"), which begins: <poem> O that Pearl of great price! have you found it? Is the Savior supreme in your love? O consider it well, ere you answer, As you hope for a welcome above. Have you given up all for this Treasure? Have you counted past gains as