Though all pearls are unique, each one usually has small imperfections on its surface described in the industry as blisters, spots or indentations.

As a pearl is produced it can develop these marks, and surface quality is judged by the number of those flaws visible on the outside of the pearl. A pearl with fewer surface markings is more rare and hence more valuable. However, like diamonds, pearls are rarely flawless.

Fine pearls have virtually no spots, bumps, pits, circles or wrinkles. High luster will often make tiny surface imperfections less visible and generally compensate for these small imperfections. Also, when the pearls are strung as a necklace or mounted on earrings, the mounting and drill holes can do much to detract from any flaws inherent in the pearl.