Mia Hanley, age 14, of Hutchinson, Kan., for her question:

WHO FIRST MADE CULTURED PEARLS?

The pearl is one of the world's most valuable gems. Most precious gems are minerals that are mined from beneath the earth, but pearls are formed inside the shells of oysters. Cultured pearls, like natural pearls, are also real pearls made by oysters.

Cultured pearls are produced by inserting in an oyster a bead made of mother of pearl. The process of making cultured pearls was developed in Japan in the early 1900s by a man named Kokichi Mikimoto. He died in 1954 at the age of 96.

Oysters make a special substance called nacre. It lines the inside of their shells. When a foreign substance, such as grain of sand or a tiny parasite, enters the shell, the nacre forming cells start to work. They cover the invading substance with thin sheets of nacre. They build successive circular layers of nacre until the foreign body is enclosed in the shell like substance, forming the pearl.

To produce cultured pearls, a special species of young oysters are planted in carefully selected oyster beds. When the oysters are 3 years old, they are taken from the beds to special plants where trained persons open the shells and insert tiny pellets.

The workers then place the oysters in wire cages that will protect them from enemies. The cages are suspended from rafts and lowered into calm, protected waters near the shore.

Twice a year attendants raise the cages and remove seaweed and barnacles from the oysters. Progress of the oyster and the care given it are recorded on small metal tags attached to the cage.

When the oyster is 7 years old it is removed from the cage and and its shell is opened. There is a valuable pearl in only about one out of every 20 oysters opened.

The cultured pearl is then washed, graded and polished before it is sent to market.

About 70 percent of all cultured pearls in the world are sold in the United States.

Cultured pearls usually can be distinguished from natural ones only by laboratory tests. The cultured pearl has a larger central body around which the layers of nacre form. It also has fewer and thicker layers of nacre.

Cultured pearls should never be taken for imitation pearls. Imitation pearls are made by man. They are usually made by coating glass beads with a substance known as pearl essence. This substance, sometimes known by its French name essence d'orient, is a creamy liquid extracted from fish scales.

In imitation pearls, the main ingredient is often obtained from herring scales. Mother of pearl is formed by the nacre secreted by certain inedible clams andoysters. It is the same substance that forms the pearl.

The mother of pearl of commerce is taken from the lining of the oyster shell. Ithas the same quality and character as natural pearl, but is formedin flat layers.  

Mother of pearl is used to make buttons and to decoarte small items such as knife handles and pillboxes.