Colorimetry Study And Color Quality Evaluation On Amazonite

In this paper,10 light blue,blueish green and green Amazonite were selected as samples.Based on the CIE 1976L*a*b*uniform color space,the X-rite SP62 integrating sphere spectrophotometer was used to measure and quantify the color of the Amazonite samples.The color parameters of Amazonite samples were analyzed to explore the internal and external factors which affect the color of the Amazonite samples.The color parameters of Amazonite were analyzed by K-means clustering method.The colors of Amazonite were divided into eight grades:A1 bright greenish blue(L*?[70.42,78.70],C*?[17.53,28.52],h°?[197.46,201.79]),A2 dark greenish blue(L*?[44.46,52.25],C*?[22.41,29.40],h°?[193.33,197.22]),A3 dark bluish green(L*?[69.40,78.92],C*?[9.45,16.24],h°?[169.96,200.89]),A4 light bluish green(L*?[47.4,57.93],C*?[11.44,18.02],h°?[166.84,197.24]),A5 dark green(L*?[45.31,51.26],C*?[15.62,23.41],h°?[154.76,170.89]),A6 light green(L*?[54.31,64.66],C*?[8.53,18.05],h°?[131.12,186.32]),A7 yellowish green(L*?[62.61,72.75],C*?[9.33,20.66],h°?[145.62,187.16]),A 8 light yellowish green(L*?[69.09,80.29],C*?[6.36,12.06],h°?[134.20,179.10]).Color levels decrease in order,A1 is the highest color level,A8 is the lowest color level.UV-vis spectra shows that there are 380 nm,640 nm and 720 nm absorption bands in Amazonite.The 640nm absorption band indicates that the electron center of Pb+is one of the color centers of Amazonite.The 720nm absorption band indicates that the 0--Pb+center is also the color center of Amazonite.LA-ICP-MS test results show that the samples contain elements,such as K,Al,Si,P,Mg,Ca,Rb,Cs,Pb,La,Pr,Sc,Y,etc.The higher the content of Rb in Amazonite is,the lower the brightness is,the higher the chroma is;the higher the content of Cs is,the higher the chroma of Amazonite is;the higher the content of Pb is,the smaller the of Amazonite is.The color of Amazonite was tested by changing illuminance and lighting source,and the influence of illumination conditions on the color of Amazonite was studied.The results showed that the best illuminance conditions of Amazonite under different light sources were different:under D65 standard light source,it is suggested that if the illumination level is 15001x,Amazonite can show more blue hue,and have high brightness and high chroma;under A standard light source,the suitable display illumination of Amazonite with blue-green tone is 10001x,and that of yellowish green-tone Amazonite is 15001x;under the CWF light source,it is suggested to set the illuminance level as 15001x to present the Amazonite with high brightness and high color.At the illumination level of 15001x,the best display illumination for Amazonite is D65 light source.