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
Daniel Pearl through music. Pearl was born in Princeton, New Jersey to Ruth and Judea Pearl. His mother is of Iraqi-Jewish descent and his father is an Israeli of Polish-Jewish descent. His family moved to the Encino district of Los Angeles, when his father took a position with UCLA. His father, Judea Pearl, is a professor of computer science and statistics, and director of the Cognitive Systems Laboratory at UCLA. He has received the Turing Award. The history of the family and its connections to Israel are described by Judea Pearl in the "LA Times" article, "Roots in the Holy Land". Pearl