摘要
以非洲几内亚褐色蓝宝石为研究对象,利用激光拉曼光谱仪、红外光谱仪、激光剥蚀等离子质谱仪及显微紫外-可见光谱仪系统探究其宝石学特征。研究表明,非洲几内亚蓝宝石主要呈褐色、少量为绿色,抛磨成0.4 mm薄片后显红褐色且色带较发育。放大观察结合拉曼光谱测试发现,蓝宝石内部含有大量包裹体且以针状包裹体居多,含有硬水铝石、金红石、黄铁矿、磁铁矿、赤铁矿、锐铁矿等。红外光谱显示明显的1990、2123、2912 cm^(-1)和3033 cm^(-1)处与硬水铝石相关的O-H振动峰,指示其未经过热处理。激光剥蚀等离子质谱仪测试显示几内亚褐色蓝宝石中微量元素Fe、Ti、Cr含量较高,深色色带与浅色色带间的Fe、Ti等微量元素含量差异较大,与深色色带内部更为富集针状包裹体有关,根据浅色色带处Fe/Ti浓度比>10,推测为玄武岩型蓝宝石。紫外-可见吸收光谱显示由Fe^(3+)导致的377、387、450 nm处吸收峰,与Cr^(3+)离子有关的556 nm处吸收宽带以及693 nm处吸收锐锋,综合说明几内亚褐色蓝宝石体色主要为Cr^(3+)导致红色,内部含有的大量褐色包裹体导致整体呈褐色。
The gemmological characteristics of sapphire from Guinea,Africa were investigated by laser Raman spectrometer,Fourier transform infrared spectrometer(FTIR),laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)and micro-ultraviolet-visible spectrometer(UV-Vis).The analytical results show that sapphires from Guinea,Africa are mainly brown,with a minor contribution of green colour.After polishing into 0.4 mm slices,they show a reddish brown colour with obvious colour bands.Magnified observation showed that there are a lot of inclusions in sapphire and most of them are needle-like inclusions.Combined with Raman spectrum test results,it shows diaspore,rutile,pyrite,magnetite,hematite,anatase and other inclusions.The infrared spectra show obvious O-H vibration peaks related to diaspore at 1990,2123,2912 cm^(-1) and 3033 cm^(-1),indicating that the sapphires were not heated.The contents of Fe,Ti and Cr in brown sapphires from Guinea are high.Fe,Ti and other trace elements between dark and light colour bands are quite different,which may be related to the enrichment of many inclusions in the dark colour band.According to the Fe/Ti ration(more than 10)in the light colour zone,brown sapphires from Guinea can be inferred as basaltic type.The UV-Vis absorption spectra show 377,387 nm and 450 nm absorption peaks caused by Fe^(3+),and 556 nm absorption broad band and 693 nm absorption sharp front related to Cr^(3+) ions.The red body colour of brown sapphire is mainly caused by Cr^(3+),and the overall brown colour is caused by a large number of brown inclusions in the interior.
作者
余丽
潘少逵
YU Li;PAN Shaokui(Gemmological Institute,China University of Geosciences,Wuhan 430074,China;Hubei Gems and Jewelry Engineering Technology Research Center,Wuhan 430074,China)
基金
国家自然科学基金-佳木斯地块岩石圈地幔的性质及演化(41973032)
中国地质大学(武汉)珠宝检测技术创新中心基金项目(CIGTXM-03-202102),文章编号CIGTWZ-2022015。
关键词
褐色蓝宝石
宝石学特征
化学成分
颜色成因
几内亚
brown sapphire
gemmological characteristic
chemical composition
colour origin
Guinea
