Five factors determine the quality of pearls: nacre, luster, surface, shape and size. The thicker nacre represents the better quality. Generally, the pearl with thicker nacre has better luster and lasts longer. More lustrous pearl represents better quality. The pearl with smoother and less blemished surface has better quality. Rounder shape represents better quality. Under same size of nucleus, the bigger pearl size represents better quality because it has thicker nacre.
Three factors determine the value of pearls:
type, quality and size. Under comparable quality, South Sea pearl has highest
value; Tahitian pearl comes the second; Akoya pearl comes the third; Freshwater
pearl comes the last. Obviously, for the same type of pearl, better
quality is more valuable. The pearl with bigger size demands higher value
under same quality.