Cultured pearls are made by artificially inserting a small bead or other foreign substance into an oyster who promptly start to cover it with nacre. It is this continuous covering for 3 to 5 years which produces the pearl.
It is based upon the oysters natural resistance to any foreign substance entering its living space which is to cover the foreign matter with a protective substance to the pearl.
The cultivation of pearls in this matter was introduced and patented by Kokichi Mikimoto in 1916.
It is ironic now that the quality of cultivated pearls rivals, if not surpasses that of the natural oyster and the Chinese are now the past maters of the art of pearl cultivation.
The Japanese were the leaders in pearl cultivation for many years but the Chinese were the first to introduce it to fresh water mussels as distinct from the salt water oyster.
Natural freshwater pearls occur in mussels for the same reason that saltwater pearls occur in oysters. A foreign material, usually a sharp object or parasite, enters a mussel and cannot be expelled. To reduce the irritation caused by the sharp object, the mollusk coats the intruder with the same secretion it uses for shell-building, nacre.
To culture freshwater mussels, workers slightly open their shells, cut small slits into the mantle tissue inside both shells, and insert small pieces of live mantle tissue from another mussel into those slits. In freshwater mussels that insertion alone is sufficient to start nacre production.
Most cultured freshwater pearls are composed entirely of nacre, just like their natural freshwater and natural saltwater counterparts.
As well as the Chinese and Japanese cultured pearls there are also the South Pacific black pearls and other colors now available to suit the many tastes and preferences.
Many qualities are also available from simple small pearls to very expensive black or rose pearls of high quality and luster
Cultivating cultured pearls have placed pearls within reach of most people now.