How is a cultured pearl produced?
[ 2006-12-22 11:39 ]
About 4,000 years ago the Chinese discovered pearls inoysters. The inside of an oyster's shell is covered with a smooth shiny coating called mother-of-pearl. When anirritant, such as a grain of sand, gets caught inside the oyster's shell it secretes layers of mother-of-pearl to protect its body by coating the irritant. The coated grain of sand becomes a pearl.
Man can force the oyster to produce a pearl by inserting an irritant into the shell. It takes the oyster two to three years to produce a good size pearl. Cultured pearls are usually not perfect, but the Japanese have discovered that if you surgically insert an irritant directly into the body of the oyster this will produce a perfect pearl.
Historically, pearl divers dove up to 80 feet with equipment no more sophisticated than nose clips. The divers could stay under water for about a minute and they scooped up the shells with their hands and put them in tubs that would float to the surface. The largest pearl ever found is reported to be four inches around and two inches long.
（英语点津 Annabel 编辑）