Feasibility study on color evaluation of jadeite based on GemDialogue color chip images

摘要

Abstract Through the calculation of gemological chromaticity, the green characters and range of chromaticity of 728 cabochon jadeite jade were determined, and then it studies and compares with GemDialogue color card images for jadeite-jade green quality evaluation. It is testified that the method is proved to be effective and the construction of emerald green quality grading system based on it is proved. First of all, with reference to China national standard GB/T 23885-2009 “Jadeite-jade Grading,” the color appearance of jadeite-jade color green was analyzed contrastively with the help of three pieces of GemDialogue color chip images G, Y2G, and B2G where CIE recommended standard light sources D65, A, and CWF, and then it is proposed that the best light source of jadeite-jade color green measuring and evaluating is standard D65 based on quantitative analysis of samples’ lightness L*, chroma C*, hue h0. Secondly, according to samples color green and five pieces of GemDialogue color chip images G2Y, Y2G, G, B2G, and G2B, jadeite-jade color was graded in seven levels from the best end “Fancy Vivid” to the last end “Very Light” with the contribution of five different overlap modes of three color masks: black/gray transparent, brown transparent, and black/white opaque. Furthermore, the high accuracy of the method is verified by clustering analysis and Fisher’s discrimination reversely. It draws conclusions that there are two evaluation methods of jadeite-jade color green; the first is the colorimetric way of GemDialogue color chip images, and the complementary is the way of Fisher functional method which sample parameters could be back substituted, and all these two methods could be extended to other green gem quality evaluation.