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. 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.
Cultured pearls come in a variety of colors from rose to black.
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.