Study On The Coloring Mechanism And Chromaticity Of Green Emerald In Myanmar

The color of jadeites is one of the important factors to measure their market value. And in the scientific research, the coloration mechanism and the differences in colorimetry are always the emphases and difficulties. In this paper, the differences of structure, composition of colorless and green Burma jadeite were studied using infrared spectrometer, spectrometer and ultraviolet-visible spectrophotometer. And the characters of different green hue jadeites’color were studied using USB2000+ fiber optic spectrometer. The main analysis is the color mechanism of jadeite, and according to the principle of colorimetry, the color of jadeite is classified quantitatively. The conclusions are as follows:(1) In infrared spectrometer testing, there has a wide absorption band at 3500cm"1; near 1080cm-1,745cm-1,960cm-1,588cm"1,664cm-1 and 530cm-1, there appear typical absorption peaks. Through the position of absorption peaks can distinguish the jadeite and omphacitic jadeite.(2) In energy spectrum testing, only Na, Al, O and Si were detected in colorless jadeite, and these elements are the main component of jadeite. Except Na, Al, O and Si, it also detected Mg, Fe, Ca and Cr in Green jadeite. The relative content of Cr, Mg, Fe and Ca can lead to the change of color.(3) In ultraviolet-visible spectrophotometer absorption spectra testing, there is a absorption peak at 437nm in all samples. Compared to the colorless jadeite, green jadeite appeared the absorption peak of Cr3+, showing that the color green is caused by Cr.(4) For light green jadeite, the reflection peak is not sharp and the reflectivity is 10%-20%, and the dominant wavelength is near 500nm. For green jadeite, the reflection peak is sharp and the reflectivity is 10%-30%, the dominant wavelength is near 530nm.(5) For green jadeite samples, when the hue angle in 195°～210° and the dominant wavelength is 491～493nm, its hue is bluish green; when the hue angle in 180°～195° and the dominant wavelength is 493～497nm, its hue is blue green; when the hue angle in 165°～180° and the dominant wavelength is 497-509nm, its hue is green; when the hue angle in 150°～165° and the dominant wavelength is 509-538nm, its hue is pan yellow green; when the hue angle in 135°～150° and the dominant wavelength is 539-553nm, its hue is yellow green.