Pearls
Guidelines to buying pearls
Natural or real pearls are made by oysters and other mollusks. A pearl is one of the few gem materials derived from a living organism. Cultured pearls also are grown by mollusks, but with human intervention; that is, an irritant introduced into the shells causes a pearl to grow. Imitation pearls are man-made with glass, plastic, or organic materials.
Because natural pearls are very rare, most pearls used in jewelry are either cultured or imitation pearls. Cultured pearls, because they are made by oysters or mollusks, usually are more expensive than imitation pearls. A cultured pearl's value is largely based on its size, usually stated in millimeters, and the quality of its nacre coating, which gives it luster.
Pearls come in a variety of sizes, shapes and colors. Some of the basic varieties include Akoya cultured saltwater pearl, freshwater cultured pearls, South Sea cultured pearl and Tahitian Black cultured pearls.
Most pearls are graded based upon size, color, shape, luster, nacre, number of blemishes, and matching. When judging pearls, it is best to lay them on a light (white or gray) color background and compare strands or individual pearls with each other.
Size
The size of the pearl is determined largely by the size of the implanted nucleus. All other things being equal, the larger the size the more rare and valuable the pearl. South Sea and Tahitian Black pearls are known for their large size ranging usually from 10 to 19mm. Akoya cultured pearls tend to be 10mm or smaller.
Color
Pearls come in a variety of colors including white, cream, pink, yellow, gold and black. Cultured pearls often have a secondary color referred to as overtone, which is traditionally rose or green in Akoya pearls and pink, blue, green, silver or gold in Tahitian black pearls. Generally speaking, Akoya pearls with a silver-white body color and rose overtone are most prized.
Shape
Perfectly round pearls are rare. The shape of a pearl can range from baroque, which is very asymmetrical, to round. The more round the pearl the greater the value, all other things being equal.
Luster & Nacre
Luster refers to how well the light reflects from a pearl back to the eye. The sharper the reflection the higher the luster. The luster depends primarily upon the thickness and the quality of the nacre. The oyster in colored waters produces higher luster. Also the longer the pearl is left in the oyster, the thicker the nacre. All other things being equal, the higher the luster the greater the value.
Number of blemishes
This refers to the quality of the surface of the pearl. Small pits and imperfections on the surface are referred to as blemishes. They can be best examined by rotating the pearl slightly. The fewer number of blemishes the higher the value.
Matching
A strand of pearls is valued based in part upon how well the pearls are matched with respect to the attributes listed above. It is important that the pearls are well matched in terms of size, color, shape, luster and blemish.