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.
|Reflections are uniformly bright and sharp.
|Slightly less defined, fairly sharp, bright reflections.
|Reflections are not clear but still fairly bright.
|Reflections are very fuzzy and weak.
|Reflections are non-existent or extremely weak.