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 (novel) his head blown off in the pearl, throws it into the ocean. Steinbeck began writing the story as a movie script in 1944, and first published it as a short story called "The Pearl of the World" in "Woman's Home Companion" in December 1945. The original publication is also sometimes listed as "The Pearl of La Paz". He expanded it to novella length and published it under the name "The Pearl" by Viking Press in 1947. As he was writing the novella version, he was frequently travelling to Mexico where the film version, co-written with Jack Wagner, was being filmed.