Cultured pearl Cultured pearl A cultured pearl is a pearl created by an oyster farmer under controlled conditions. Cultured pearls can be farmed using two very different groups of bivalve mollusk: the freshwater river mussels, and the saltwater pearl oysters. A pearl is formed when the mantle tissue is injured by a parasite, an attack of a fish or another event that damages the external fragile rim of the shell of a mollusk shell bivalve or gastropod. In response, the mantle tissue of the mollusk secretes nacre into the pearl sac, a cyst that forms during the healing process. Chemically speaking, this
The Thirteenth Pearl The Thirteenth Pearl The Thirteenth Pearl is the fifty-sixth volume in the Nancy Drew Mystery Stories series. It was first published in 1979 under the pseudonym Carolyn Keene. The actual author was ghostwriter Harriet Stratemeyer Adams. "The Thirteenth Pearl" is the end of the original 56-book series published by Grosset & Dunlap. Subsequent volumes were published by Simon & Schuster. Nancy Drew is asked to locate a missing pearl that is unusual, but very valuable. She soon learns that dangerous people are responsible for the theft. They begin harassing her at home and it intensifies when Nancy and her father