The cultured pearl is basically a 20th-Century product. Several men tried o develop a method for producing spherical pearls, and the names Nishikawa, Mise, and Mikimoto are prominent in this regard. After a complicated patent settlement, Mikimoto emerged dominant in the cultured pearl industry.
A cultured pearl is produced by inserting a mother-of-pearl bead into the tissues of a pearl-producing mollusk. The mollusk treats the bead as an irritant and deposits a nacreous coating over it. thus, the basic difference between a natural and a cultured Pearl is the nature and size of the nucleus particle, and the way the pearl originates.
Blister pearls are produced by inserting a half-bead against the shell of the mollusk. After a layer of nacre has been deposited over the bead, the whole formation is cut out and the nacreous dome cemented onto a mother-of-pearl bead. The result is called a mabe pearl.
Biwa pearls are produced at Lake Biwa, Japan using freshwater clams. Biwa pearls are irregular in shape, but have good color and orient. They are distinctive because they have no nucleus; instead of a bead, small squares of tissue are inserted into the clam. The pearls that develop require three years to grow.
Japan is the world’s leading producer of cultured pearls. The usual shapes produced are the baroque, round, button, oval, pear, and egg; very few cultured pearls are perfect spheres. Of all gems, pearls are the most difficult to authenticate. The only truly reliable test involves the use of an x-ray machine, which can be dangerous in unskilled hands. Fine cultured pearls are, to the eye, indistinguishable from genuine peals, and simple tests are not reliable in all cases.
The qualities that determine the value of genuine Pearls also apply in the case of cultured pearls. Generally prices of cultured pearls are lower, but even a strand of these may bring a price in excess of $100,000.