改色处理紫红色钻石的光谱学特征及鉴定方法

Spectroscopic Characteristics and Identification Methods of Color-Treated Purplish Red Diamonds

以市场上销售的国内改色紫红色圆刻面型钻石为研究对象,通过对其光谱学特征进行分析,确定了此类紫红色改色处理钻石的鉴定。样品颜色呈现不同饱和度的紫红色,净水称重法测试比重为3.52,放大观察,样品DR-2与DR-3的部分刻面光泽较弱,显示了未被重新抛光的严重烧蚀区域,石墨化沿内应力断裂明显,其表面可能经过高温高压处理。365nm长波紫外下,均呈现蓝色、橙红色、黄色和绿色混合的白垩状荧光外观,无磷光现象,而天然紫红色钻石为蓝色荧光或无荧光。宽频诱导发光图像仪GV5000深紫外下均呈现橙红色和蓝色混合荧光,无磷光现象。红外光谱中红外区均显示集合体氮相关的A中心和B中心,归类为IaAB型,且具有H1a辐照退火相关的特征峰,红外光谱近红外区均显示H1b,H1c辐照退火相关的特征峰与H_(2)中心的特征峰。紫外可见近红外分光光度计均显示明显的NV-中心,H_(2)中心和806 nm吸收峰,400~460和570 nm宽带处反射率的变化分别与N_(3)中心和NV^(0)中心相关,明显的NV-中心在天然紫红色钻石中极少发现,H_(2)中心指示可能经过高温高压处理,可见光范围内对红光和蓝光的吸收较弱,所以呈现为紫红色外观。三维荧光光谱和光致发光光谱均显示出N_(3),H_(3),H_(4),NV^(0),NV-相关的发光中心,N_(3)贡献蓝色荧光,H_(3)和H_(4)贡献黄绿色荧光,NV^(0)与NV-贡献橙红色荧光。综合分析,三颗样品均为天然成因的钻石,后期经过高温高压,辐照,退火等多重处理,其紫红色主要由N_(3)中心,NV^(0)中心与NV-中心共同贡献。

Based on the analysis of the spectral characteristics of round faceted color-treated purplish-red diamonds from the domestic market,the identification of this kind of diamonds is confirmed.The sample diamonds are purplish-red with different saturation,and the specific gravity of the hydrostatic weighing method is 3.52.Magnification observation shows that partial facets with the weaker luster of DR-2 and DR-3 have ablative areas that are not re-polished,and graphitization is also obvious along with internal stress fracture,both indicating that samples have been treated with high temperature and high pressure.Under the long-wavelength ultraviolet of 365 nm,the chalky fluorescence appearance of blue,orange-red,yellow and green is mixed,and the phosphorescence phenomenon is absent,which is different from the blue fluorescence or no fluorescence phenomenon of nature-colored purplish-red diamonds.Under GV5000,orange-red and blue mixed fluorescence is observed,and the phosphorescence phenomenon is absent.In the mid-infrared spectra,A center and B center,which show aggregation nitrogen correlation,are classified into IaAB type and have characteristic peaks related to H1a radiation annealing,while in the near-infrared spectra,characteristic peaks of H1b,H1c related to irradiation annealing and characteristic peaks of H_(2) center are shown.UV-VIS-NIR spectra shows obvious NV-,H_(2) and 806 nm absorption peak;400~460 and 570 nm broadband reflectivity changes are associated with N_(3) and NV^(0) respectively.Obvious NV-is rarely found in natural purplish-red diamonds and H_(2) indicates diamonds may be treated with high temperature and high pressure.Furthermore,the low absorption of red light and blue light results in purplish-red appearance.Three-dimension fluorescence spectra and photoluminescence spectra show that N_(3),H_(3),H_(4),NV^(0) and NV-luminescence centers.N_(3) contributes blue fluorescence,H_(3) and H_(4) contribute yellow-green fluorescence,and NV^(0) and NV-contribute orange-red fluorescence.According to the comprehensive analysis,the three samples are all diamonds of natural origin that have undergone multiple treatments such as high temperature and high pressure,irradiation and annealing,etc.,and the purplish-red color is mainly due to the joint contribution of N_(3),NV^(0) and NV-.