What qualities* make one pearl more valued than another?
Size: Size speaks for itself; larger simply is more valuable, all other things being equal.
Shape: Round is the rarest and is the most valuable. After that, off-round, oval, drop, buttons, coins, freeform are an example of the progression of the shape. The further from round the lower the value.GIA classifies shapes into 3 categories: spherical, symmetrical & baroque.
Color: White is the universal color. In Asia & the USA pink-white is the ultimate. Other favored natural colors are pink, golden pink, lavender, purple, black, etc. Many pearls are enhanced with dyes, irradiation and other treatments. Dyed pearls have a lesser value than those with natural colors.
GIA classifies pearl color as having 3 characteristics:
Luster: This is the most important quality in evaluating the beauty of a pearl. The iridescence, the life of the pearl, the shimmer, glow, and the luminosity of the pearl all come together here. Luster is closely related to orient.
GIA has 4 categories for luster:
Surface quality: Evenness of the surface, with no undulating undercurrents to distract the eye.
GIA classifies this into 4 categories:
Nacre quality: Interrelated with the other two. Thickness & quality of nacre are selling points for fresh water pearls. The quality ranges from acceptable to chalky.
Matching: A brilliant matching pair is more difficult find than a single gem. Look for overall uniformity in color, shape, finish etc. in a strand or suite.
Uniqueness: This can be any unusual combination of the forgoing factors.
Provenance: Previous ownership, from fame to notoriety enhances the value of a pearl. It is the legacy of the pearls detailing its journey from the past to the present. Provenance is related to Branding.
* These qualities apply to all natural and cultivated pearls.