Claudette Colbert was draped in pearls in her depiction of Cleopatra in the 1934 movie of the same name with Henry Wilcoxon playing Mark Antony. Click photo for larger image. Related article Classic string of pearls stretches into a new millenium

A natural pearl forms when an irritant works its way into a particular species of oyster, mussel or clam. The mollusk secretes a fluid to coat the irritant. Layer upon layer of this coating is deposited on the irritant until a lustrous pearl is formed.

A cultured pearl undergoes the same process, although the irritant -- usually a piece of shell or mother-of-pearl bead -- is surgically implanted and the core is much larger than a natural pearl.

When shopping for cultured or natural pearls, look for color, luster, shape, size and surface.

The color should be even, no matter what the shade. Perfectly round pearls are rare. The pearls should appear clean and without bumps or pits. The longer the pearl is left in the oyster to grow its nacre casing (over the irritant) the higher the luster; pearls that appear dull are low in quality.

As first lady, Jackie Kennedy was seen wearing triple strands, not all of them real. Click photo for larger image.

If you choose white pearls, they should never be whiter than your teeth, which could make you look older.

Caring for pearls

Pearls should be the last thing you put on and the first thing you take off. Never let hair spray, perfume or cream come in contact with pearls; the substances can wear away the nacre over time.

Wash pearls in mild soapy liquid like dish detergent, rub them in your hands to get the grease and body oils off and then put them on a paper towel to dry.

Store them separately from other jewelry, which can scratch them. They're best placed in a fabric pouch or fabric-lined box.

Sources: www.style.com; www.pearls.com; Post-Gazette research