Most pearls today are cultured pearls, which are created by placing an irritant in the oyster and stimulating the deposit of nacre. Different types of oysters or freshwater mollusks generate pearls of different size, color and other qualities.
When purchasing pearls, look for sets in which the individual pearls all match. Cultured pearls are rated for five different qualities:
A pearl with fewer imperfections on its surface is said to be a “cleaner” pearl. All real pearls (natural or cultured) will have some imperfections, but value increases the fewer and less noticeable they are.
Pearls are described as a main color (white, black, or yellow) with an undertone color of pink, rose, or green. Pearls can also be dyed any shade to satisfy your taste.
LUSTER and ORIENT:
Luster refers to the sharpness and intensity of reflections on the pearl’s surface, and orient has to do with the spectrum of colors visible within the pearl. Pearls with higher ratings for luster and orient are more valuable.
The most commonly prized shape is a sphere. Generally, the more perfectly spherical a pearl is the more valuable it will be. Some symmetrical imperfections can also be desirable, though, like the teardrop pearls that are sometimes used for earrings and pendants.
Pearls are measured by diameter in millimeters. The larger the pearl, the higher the price.