Facts about Pearls

• Pearls form inside living bivalve mollusks.


• Bivalve mollusks have a shell with two parts and a muscle that allows the mollusk to open and close the shell. Oysters are the most common mollusk to naturally make pearls, but mussels and clams can also make pearls.


• The mollusks feel an irritation caused by sand or other material. In response, the mollusks form material around the sand. It grows larger and larger as new coatings are applied.


• The coating material that makes up a pearl is known as nacre or "mother of pearl". It is material like calcium carbonate, which is very tough. Like all calcium carbonates, pearls can be destoyed by acid.


• Mother of pearl is also the material that coats the inside of many oyster and clam shells.


• When this process occurs naturally, the result is a natural pearl, which is very valuable.


• Pearls are sold by the karat. The cost is based on the size, shape, color, origin, perfection and luster (if it is shiny). A large, perfect natural pearl from the South Pacific is worth over $30,000.


• Most bivalve mollusks make pearls, however, not all pearls are attractive. Pearls occurring naturally are rare.


• The largest supplier of pearls is Lake Biwa in Japan.


• Pearls that grow attached to the animal's shell are called blister pearls.


• Cultured pearls are grown with the help of people. A person places a tiny piece of glass or a plastic bead inside the mollusk. The cultured pearl then takes about 4 years to grow.


• Cultured pearls are valuable, but not as valuable as natural pearls.


• With advancements in plastics, people can now make "fake pearls", which look real to an inexperienced person.