CULTUREDPEARL
Cultured pearl
A cultured pearl is a pearl created by a pearl farmer under controlled conditions. 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 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. It is a myth that a grain of sand or grit can cause a ...The above text is a snippet from Wikipedia: Cultured pearl
and as such is available under the Creative Commons Attribution/Share-Alike License.