Pearl Luster

Pearl Luster is defined by the sharpness and brightness of reflections as seen on the surface of a pearl. The Gemological Institute of America classifies pearl luster into five grades.

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Grade Reflections/Observations
Excellent Reflections are uniformly bright and sharp.
Very Good Slightly less defined, fairly sharp, bright reflections.
Good Reflections are not clear but still fairly bright.
Fair Reflections are very fuzzy and weak.
Poor Reflections are non-existent or extremely weak.