Pearls are made of the same material as the mother-of-pearl lining in the shell of the oyster. The body of the oyster is very tender, so to protect itself the oyster secretes this mother-of-pearl lining to provide a smooth surface against the body. When an irritating object, such as a grain of sand, manages to get inside the oyster’s shell, the oyster coats it with layer after layer of mother-of-pearl and this becomes a pearl. When this happens naturally, the petal may be perfectly shaped. But man has found a way to help the oyster in the making of pearls. A grain of sand is inserted between the shell and the outer skin of the oyster. After two or three years, when these shells are taken from water and opened, a pearl is found inside. These are called ‘cultured’ pearls, and are usually not perfectly shaped.
The largest pearl ever found is said to have been two inches long and four inches round. Because real pearls are so expensive, most of us buy artificial pearls.