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
Pearl of Lao Tzu Pearl of Lao Tzu The Pearl of Lao Tzu (also referred to as Pearl of Lao Tze and previously as Pearl of Allah) used to be the largest known pearl. The pearl was found in the Palawan sea, which surrounds the island of Palawan in the Philippines, and was found by a Filipino diver. It is not considered a gemstone pearl, but is instead known as a "clam pearl" or ""Tridacna" pearl" from a giant clam. It measures 24 centimeters in diameter (9.45 inches) and weighs 6.4 kilograms (14.2 lb). The pearl came from Brooke's Point, Palawan in the Philippines.