And remember. pearls are ecologically friendly- their hosts need clean water to be happy. We have learned this the hard way from Lake Biwa and other such examples that lost very valuable pearl businesses when the lakes or sea waters got too poisoned.
Also we used to have many rivers in America just bursting with freshwater mussels of many vareties that produce pearls of many colors- Pearling was part of Sunday riverside picnics for generations in America, but we have lost most of this national treasure through overfishing in the late 19th century, then pollution in the 20th.
Many species of American mussels (aka "unios") remain endangered, though the mollusc scientists continually express amazement at how much the little guys can take, before they die. Mussels actually filter water in their habitats and keep it clean of organic debris, but they can't do anything about chemically poisoned water. The unio (mollusk) scientists have to wear all kinds of scuba and other gear to protect them from the waters where they study unios! They often get poisoned themselves, with wierd and icky reactions to their skins and other organs from swimming in chemically polluted waters.
To learn more about these intrepid biologists, sign up for
Unio Listserve, a kind of forum for the study of unios
in situ. Many colleges and universities have professor and student members, though it is open to the public- especially those who are interested in growing mussels in domestic situations, ie ponds and tanks.
