In jewelry I work mainly in pearls and fine gems in 14kt gold settings. There is no universal agreement on pearl grading. The following grading for pearls is generally accepted in the industry:
AAA: The highest-quality pearl, virtually flawless. The surface will have a high luster and at least 95% of the surface will be free from any type of defect.
AA: The surface will have a very high luster and at least 75% of the surface will be free from any type of defect
A: This is the lowest jewelry-grade pearl, with lower luster and/or more than 25% of the surface showing defects
Spherical: round or near round
Symmetrical: pearls that look the same on each side if you divided them in half
Baroque: irregularly shaped
GIA pearl color classification characteristics-
Body Color: the dominant overall color of a pearl
Overtone: One or more translucent colors that appear over a pearl's body color
Orient: Iridescent, rainbow colors shimmering on or just below a pearl's surface
This is the most important quality in evaluating the beauty of a pearl. The iridescence, the life of the pearl, the shimmer, glow, and luminosity of the pearl all come together here. Luster is closely related to orient.
Excellent: reflections are bright and pinpoint sharp
Good: reflections are bright but not as sharp, slightly matte finish
Fair: reflections are hazy and blurred
Poor: reflections are diffused and appear chalky and dull
Clean: virtually blemish free
Lightly Blemished: minor surface irregularities
Moderately Blemished: noticeable surface irregularities
Heavily Blemished: obvious surface irregularities Grading systems for gems vary according to their use. Gems that are used for beads are usually of lower quality than gems used in rings, earrings, etc.