The pearl, symbol of purity, virtue and modesty, is one of the most precious types of jewelry. Pearls have been harvested and worn for more than 4,000 years.

Black cultured pearls can come from a variety of sources. The rarest are those that come from a large black-lipped oyster found in the South Seas. These oysters create large, silver-gray to black pearls that can have other colors as overtones; a peacock green is the most valuable overtone.

Given the rarity of South Seas black cultured pearls, there are enhanced black cultured pearls that can be used as an alternative. These often come from China and Japan, and are actually white cultured pearls that are either exposed to radiation or dyed all the way through using a process called French dying. French dying will produce an even, strong color that lasts for years. However, they are real cultured pearls and need to be handled with the same care as naturally colored pearls.

Recently, techniques have been developed to culture pearls in freshwater mollusks. These pearls are sometimes called Biwa pearls after the lake in Japan where they were first developed. Today that name should only be used for cultured pearls from Lake Biwa.

Freshwater cultured pearls are cultivated around the world, including Tennessee, and come in a variety of shapes and sizes. Some freshwater cultured pearls are spheres that are used like other round pearls, and some are buttons used to accent jewelry. Still others are blister shapes called Mabé, which are often used in earrings and other pieces with closed backs.

Most cultured pearls on the market today are white pearls, which are fairly translucent and can have undertones of pink, yellow or other colors. These colors can be natural, but to find an entire string of cultured pearls in the same shade, you may have to consider dyed or irradiated pearls. The particular shade should be chosen based on preference and what best complements your skin tone. If you are buying a string of cultured pearls, make sure there are knots between the individual pearls to prevent rubbing and to ensure that only one cultured pearl will drop if the string breaks.