LUSTRE: Lustre is a combination of surface brilliance and a deep seated glow. The lustre of a good quality pearl should be bright and not dull. You should be able to see your own reflection clearly on the surface of a pearl. Any pearl that appears too white, dull or chalky indicates low quality.
SURFACE: Cleanliness refers to the absence of disfiguring spots, bumps or cracks on the surface of a pearl. The cleaner the surface of the pearl, the more valuable it will be.
SHAPE: Since cultured pearls are grown by oysters in nature, it is very rare to find a perfectly round pearl. However, the rounder the pearl, the more valuable it is. Baroque pearls, which are asymmetrical in shape, can be lustrous and appealing, and often cost less than round pearls.
COLOR: Cultured pearls come in a variety of colors from rosé to black. While the color of a pearl is really a matter of the wearer’s preference, usually rosé or silver/white pearls tend to look best on fair skins while cream and gold toned pearls are flattering to darker complexions.
SIZE: Cultured pearls are measured by their diameter in millimeters. They can be smaller than one millimeter in the case of tiny seed pearls, or as large as twenty millimeters for a big South Sea pearl. The larger the pearl, other factors being equal, the more valuable it will be. The average sized pearl sold today is between 7 and 7.5 millimeters.