Color Quantification Of Gem Corundum

Color as an important property in gemstones,especially in color stones,is often placed in the first element when evaluating the value of gemstones.There are two main varieties of gem-quality corundum: ruby and sapphire.Rubies and sapphires have occupied an important position in the jewelry market since ancient times.Therefore,gemologists pay a close attention to researching rubies and sapphires,and these studies have been regarded as a hot topic in jewelry industry.Gem-quality corundum has a wide range of colors,including almost all hues in the visible spectral range.Previous researcher pay much attention to color origin of ruby and sapphire,because they want to solve the problem related to testing and also want to provide some information in guiding heat-treatment experiment.However,few researcher devoted themselves in color quantification of gem-quality corundum.In fact,the color quantification of gem-quality corundum has important significance for classifying different commercial types and detecting whether it has been during treatment or synthetic varieties.Moreover,it could be also help us precisely control the color of corundum when did heat treatment experiment.In this thesis,some high-quality synthetic corundum and some natural yellow sapphire with high Fe content were selected for UV-Vis,laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)and Digital photography analysis.At the same time,most of the samples were precisely oriented in order to obtain spectra and color features in different directions.The whole experiment was completed in four parts.Firstly,the sample was precisely cut with the crystal orientation equipment,and the sample image and polarized UV-Vis spectral data(o-ray,e-ray)were collected;secondly,using LA-ICP-MS to collect the trace element data from sample;next,the quantitative color calculation of a single chromophore was utilized by combining trace element data and UV-Vis spectra;finally,based on gem-quality corundum color calculation program,we have calculate the color characteristics of multiple chromophores combination with different proportions.The research results are as follows:1.The color characteristic calculation of each single chromophore in corundum is realized.2.Explain why Fe absorption in sapphire does not comply with Lambert Beer’s law.3.The effectiveness of different chromophores in corundum is compared quantitatively.4.The color characteristic calculation of multiple chromophores combination in corundum is realized.5.Cr and V may play a role in causing color change effect in color change sapphire(from blue to violet).