A Study On The Chromaticity Of Ruby

According to the principle of colorimetry, the reflection spectra and chromaticity parameters of ruby are measured by the USB2000+ fiber spectrometer, which is made by United States Ocean Optics company. And chemical compositions of ruby samples are analyzed by EDXRF.The conclusions of the research are obtained as follows:(1) The main chemical component of ruby is Al2O3, and also contains Cr, Fe, Ti, K, Ca, Mg, Ga and other trace impurity elements. Cr is the main color causing element, with the content of Cr increased, resulting in color from pink to bright red blood changes. At the same time, Fe, Ti ions also have a certain degree of influence on color, are the major cause of ruby purple tone, and also makes the color deepened;(2)The results of the experiment illustrate that the ruby has the 694nm obvious reflection peak generally, when ruby is more and more thick along with the purple tone,475nm place’s reflection peak is more and more obvious; the ruby only has the complementary wavelength generally, also complementary wavelengths range usually in green wavelength range;(3) Red hue of ruby is mainly caused by the d-d transition of Cr3+’s electrons.Blue hue as the mixed hue in ruby is caused by the charge transfer Fe2+-Fe3+ and Fe2+-Ti4+. The d-d transition of Ti3+’s electrons makes ruby samples with purple tones. The above factors cause the ruby samples’color deeply dark;(4)Through the complementary wavelength and hue angle, the main tone of the color of ruby can be distinguished:When the hue angle in 0°～18° and the complementary wavelength is 490～496nm, the hue is red;when the hue angle in 342°～360° and the complementary wavelength is 497-509nm, the hue is pink;when the hue angle in 324°～342°and the complementary wavelength is 509-542nm,the hue is purple red;(5)Common ruby color grading system in uniform color space can be divided into five levels,The levels are from I to V, which the chromaticity parameter of the highest level is hab*∈E(0°,18°),C*∈(20-23),LG(38-45).