Pearls: The Treasures of the Sea

Pearl, the birthstone for June, is among the most timeless, classic and treasured of all gems. Throughout history, these noble gems have been associated with wisdom, wealth, purity, romance and mystery. The ancient Egyptians were buried with them. In Rome, pearls were considered the ultimate symbol of wealth and status. The Greeks prized them for their beauty and association with love and marriage. Medieval knights wore them in battle as a talisman against injury. And during the Renaissance, some European countries banned all but nobility from the right to wear them.
It's hard to believe that such a luscious, beautiful gem comes from such humble origins. A natural pearl starts out as a grain of sand or microscopic worm that works its way into an oyster and cannot be expelled. To protect its soft body from this irritant, the oyster secretes a smooth, hard crystalline substance called nacre. Layer upon layer of nacre coats the foreign object and hardens, ultimately forming a pearl. In general, the thicker the nacre, the richer the "glow" of the pearl - which can greatly enhance its value.
Although early pearl gathering depended on divers braving the oceans' depths to retrieve these treasures, the vast majority of pearls today are grown, or cultured, on pearl farms by surgically inserting a small shell bead, or nucleus, into the mantle of an oyster.
Even though pearls are harvested en masse on pearl farms, producing a quality pearl is an extremely rare event. It is estimated that half of all nucleated oysters do not survive - and of those that do, only 20% bear marketable pearls.
Pearls - the recommended gift for couples celebrating their third and 30th wedding anniversaries - are cultured in a variety of sizes, shapes, colors and kinds:

* Akoya pearls are the classic round pearls found in most quality pearl jewelry. They are mainly grown in the waters off Japan. They come in a range of hues, including white, cream, pink and peach.
* White South Sea pearls are grown in Australia, Indonesia, the Philippines and other areas of the South Pacific and are prized for their large size.
* Tahitian pearls, grown in French Polynesia, can be very large and come in a range of natural colors from gray to black to green to purple. Because of their large size and unique dark colors, they command very high prices.
* Mabe pearls, grown in Japan, Indonesia, French Polynesia and Australia, are usually flat-backed because they form against the inside shell of the oyster rather than within the oyster's body. They are often used in earrings and rings.
* Freshwater pearls are grown in bays, lakes and rivers primarily in Japan, China and the United States. They are often irregularly shaped, of various colors, and are less lustrous than saltwater cultured pearls hence, they are substantially cheaper.

When shopping for pearls, the five factors that determine value are luster (surface brilliance); surface cleanliness (absence of spots, bumps or cracks); shape (generally, the rounder the pearl, the higher its value); color (pearls come in virtually every hue of the rainbow, and a few others, too); and size (the average pearl sold is 7-7.5 millimeters, but these gems can be as small as 1 millimeter or as large as 20 millimeters). High-quality pearl strands will feature pearls well-matched in these characteristics.
Because pearls are soft, ranking only 2.5-4.5 on the Mohs scale for hardness, they require special care. Natural oils from the skin, as well as hair spray, lotions and cosmetics, can dull their luster. Like other jewelry, they should be cleaned with a soft damp cloth and stored in cloth or cotton away from other jewelry to prevent scratching. Also, avoid allowing your pearl to come in contact with harsh chemicals, which can erode its surface. And if worn frequently, pearl necklaces should be brought to a jeweler once a year for re-stringing to prevent strand breakage.