Metamerism Appreciation of Jadeite-Jade Green under the Standard Light Sources D sub(65), A and CWF

We tested 288 pieces of the polished cabochon jadeite-jade with high quality green and smooth surfaces using the colorimeter Color i5 based on the CIE 1976 L*a*b* uniform color space. The color changes after alternating three CIE standard light sources D sub(65), A and CWF were compared, and the degree of metamerism was evaluated. The results show that the CIE standard light sources D sub(65), A and CWF increase the chroma of green and turn bluish green into vivid green, which are similar or to nearly colorless and transparent glass-like samples with fine textures. When the three light sources were individually alternated, the lightness of the jadeite-jades showed little change, but the tone changed significantly. Metamerism occurred only in 3 pairs among the 16 samples that were selected by cluster analysis for quality, and the metamerism colors were highly consistent of L* sub(D65)(43.47, 46.75), C* sub(D65)(65.20, 68.80) and ho* sub(D65)(138.10, 140.23). We can conclude that the jadeite-jade green gradually turns to blue when the color temperature of the light source increases. But when considering both the light sources and the samples, D sub(65) is more suitable to be the light source of jadeite-jade green when compared with the light sources CWF and A. Compared with the CIE standard green and high chroma green, high-quality jadeite-jade green has a slight yellow tone, low lightness and high chroma. The special metamerism index decreased to 1 when the light source alternated among D sub(65), A and CWF. Therefore, the color of jadeite-jade green might be slightly influenced by alternating of the light sources.