The Research On Metamerism Of Bluish-voilet Tanzanite While Illuminators Altered

Assessment of the color is always a great important aspect of color-gem industry, In the case of jewelry industry, there is already a set of relatively and perfectly color evaluation system of diamonds, while the color evaluation system of the emerging bluish-violet tanzanite, now can only rely on subjective experience which carried on the observation, lacking of the objective, unified evaluation standard of measurement. There are only few pieces of predecessors’ research of tanzanite, of opaque zoisite varieties, failed to resolve the actual color evaluation system of the bluish-violet tanzanite in classification and trade, its effect is not very good. The metamerism of bluish-violet tanzanite is obviously, it haven’t been considered ever before.This article uses the Color i5color measurement instrument, based on CIE1976L*a*b*uniform color space, with the basic gemological and color test of50bluish-violet tanzanite samples, and compared these with similar blue gems like sapphires and blue synthetic spinels, telling the difference by colorimetric data among the three. Under three kinds of lighting (D65, A, CWF) of each color data analysis shows that D65can show the true color of the bluish-violet tanzanite, and it can be used in the color grading of bluish-violet tanzanite in laboratory; A and CWF is suitable for commercial lighting light source, enhancing the red hues of bluish-violet tanzanite, while improving the visual effect.The tanzanites are selected to analysis the metamerism, with light source spectral power distribution and bluish-violet tanzanite related to the reflectance curve, it directly determines the sample can reflect or absorb which wavelengths of light, and the reflectance curve of tanzanite, the greater the similarity degree of the intersection curve, after changing light source the color change smaller, its color is more stable.From50bluish-violet tanzanite picked out4samples, analyzing the color and metamerism, found that from D65into A, tanzanite’s color change from blue to purple, more fully shows special violet tones of tanzanite, getting a better color appearance.