When a tiny foreign object becomes trapped in an oyster, the object is coated with layers of a smooth, cystalline substance known as nacre to reduce the irritation. This natural response produces the luminescent gems we know as Pearls.
Cultured Pearls, like flowers grown in a greenhouse, are gently guided through the cultivation process. An irritant, most often a spherical section of a clam shell and mantle tissue is deliberately inserted into an oyster, triggering its natural instinct to produce nacre. Since this method was perfected in the 1920s, natural Pearls have become extremely rare. Due to economic pressures and water pollution, virtually all new Pearls on the market today are cultured.
Pearls occur in a spectrum of shades. The major color classifications are white, pink, silver, cream, gold and black. Fine pearls will also have an "overtone," or secondary color that appears toward the outside of the pearl. This overtone is usually rosé, green or blue. Traditionally, cultured pearls with pinkish white or white rosé coloring are the most highly prized. In recent years, though, there has been a resurgence of interest in more unusual shades. Whatever the color, it should appear to emanate from deep within the pearl.
More than any other factor, size determines price. Pearl size is the result of the implanted nucleus plus the thickness of the nacre, which grows layer by layer. Be aware that a large pearl is of little value if it lacks nacre thickness. A thinly coated pearl will crack, discolor and become worthless. Thicker nacre equals a more beautiful and lustrous pearl. Nacre thickness can be verified only by an expert.
A pearl, like any product of nature, will have imperfections. Small marks on the surface are to be expected, but they should be minimal. Quality pearls should be free of large pits or blemishes.
Luster refers to the surface shine that gives pearls their glowing beauty. To check luster, stand with the light to your back. The sharper the reflection of light in the pearl, the higher the luster and more rare the pearl.
Perfectly round pearls are the most rare, and therefore the most valuable. While most cultured pearls are basically round, only about one percent are perfect spheres. To check a strand, roll it on a flat surface. The movement should be even and smooth. Baroque pearls, which are irregular in appearance, are also quite sought-after for their unique look.
Layers of nacre produce rainbow-like colors that appear to move over the surface of the pearl. This effect is extremely rare, appearing only in a small percentage of round pearls and in certain types of mabe and Baroque pearls.
In any piece of jewelry, the pearls should be carefully matched for size, shape, surface, color and luster. Visible variations detract from both the beauty and the value of the strand or pair.
Akoya ~ Cultured saltwater pearls produced around the islands of Japan.
Baroque ~ A style of pearls that are irregularly shaped and often feature ridges or protrusions.
Freshwater ~ Grown in mollusks found in freshwater lakes and rivers.
Mabe ~ Half-sphere pearls cultured against the inside shell of the oyster.
South Sea Keshi ~ Irregularly shaped pearls that unexpectedly grow alongside cultivated pearls in the mollusk.
South Sea ~ Cultured in warm salt waters, South Sea pearls can be exceptionally large and are generally white, golden or black. Black pearls are commonly referred to as "Tahitians" and range from light gray to very dark gray to black with a broad spectrum of overtone colors.