Because it is difficult to classify pearls refering to their physical measured quantities, we propose the following method of classification. The spectral reflectance of pearls relative to a standard metal sphere is determined at eight selected wavelengths by the spherical dome type reflectometer developed by us. From the measured spectral reflectances, two evaluation func-tions are defined as D
(580)-D
(450) for saturation, and as D' for lightness. Using these evalua-tion functions, we could sort 72 pearls into three different color groups; black, silver and cream, sorted by an experienced pearl-connoisseur.
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