Animal World

Mollusks and Echinoderms

How are pearls created?

Pearls are formed in saltwater oysters and freshwater clams. There is a curtainlike tissue called the mantle within the body of these mollusks. Certain cells on the side of the mantle toward the shell secrete nacre, also known as mother-of-pearl, during a specific stage of the shell-building process. A pearl is the result of an oyster’s reaction to a foreign body, such as a piece of sand or a parasite, within the oyster’s shell. The oyster neutralizes the invader by secreting thin layers of nacre around the foreign body, eventually building it into a pearl. The thin layers are alternately composed of calcium carbonate, argonite, and conchiolin. Irritants intentionally placed within an oyster result in the production of what are called cultured pearls.


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