The quality of a pearl is determined by a combination of several elements.
Surface is the thickness of the nacre. The thicker the nacre, the higher the quality of the pearl.
Generally, the closer to a true sphere, the higher the quality of the pearl. However, non-spherical pearls have an inherent appeal that many people prize in a piece of jewelry.
Flaws naturally arise in the course of a pearl’s formation, but the fewer the number of flaws, the better the quality.