埃塞俄比亚欧泊微结构及变彩成因探讨
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摘要
埃塞俄比亚欧泊具有较独特的变彩,通过测试不同变彩的埃塞俄比亚欧泊样品的色斑特征、物相组成及微观形貌,分析其微结构差异,探究不同变彩产生的原因。结果表明,埃塞俄比亚欧泊具有不同于其他产地的指状变彩,孔隙度相对较高。各种变彩的欧泊物相测试结果基本一致,为具有一定结晶度的欧泊。X射线粉末衍射分析、红外光谱、拉曼光谱测试结果均表明其为Opal-CT型欧泊(α-方石英和α-鳞石英交互生长,且占支配地位的是高度无序排列的α-鳞石英)。扫描电子显微镜测试结果表明,埃塞俄比亚欧泊主要为层状结构,二氧化硅小球紧密无规则排列,小球直径约为10~30nm;蓝紫色单色变彩欧泊中可见直径80~100nm小球堆积,不同变彩的欧泊微观形貌存在一定差异。变彩成因可能为薄膜干涉或者瑞利散射所致。
The play-of-colour of Ethiopian opal is very different from the opal from the other localities.In this paper,we compared the microstructure differences of Ethiopian opal and analyzed the cause of play-of-colour.The results showed that Ethiopian opal has characteristic digit pattern and its porosity is relatively high.The Ethiopian opal is crystallinity opal in terms of phase composition.XRD,FTIR and Raman spectroscopy tests showed that Ethiopian opal is Opal-CT type opal with low temperature squamous quartz and low temperature square quartz(α-cristobalite).Scanning electron microscopy result revealed that Ethiopian opal is layered structure,with consisting of silica sphere(10-30 nm in diameter)arranged closely and irregular.Opal with blue and purple colour spot has sphere 80-100 nm in diameter.It concluded that the origin of the iridescence of Ethiopian opal is mainly caused by the interference of light from the internal layers,accompanied by a certain degree of Rayleigh scattering.
The play-of-colour of Ethiopian opal is very different from the opal from the other localities.In this paper,we compared the microstructure differences of Ethiopian opal and analyzed the cause of play-of-colour.The results showed that Ethiopian opal has characteristic digit pattern and its porosity is relatively high.The Ethiopian opal is crystallinity opal in terms of phase composition.XRD,FTIR and Raman spectroscopy tests showed that Ethiopian opal is Opal-CT type opal with low temperature squamous quartz and low temperature square quartz(α-cristobalite).Scanning electron microscopy result revealed that Ethiopian opal is layered structure,with consisting of silica sphere(10-30 nm in diameter)arranged closely and irregular.Opal with blue and purple colour spot has sphere 80-100 nm in diameter.It concluded that the origin of the iridescence of Ethiopian opal is mainly caused by the interference of light from the internal layers,accompanied by a certain degree of Rayleigh scattering.
引文
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[8]Kihara K,Hirose T,Shinoda K.Raman spectra,normal modes and disorder in monoclinic tridymite and its higher temperature orthorhombic modification[J].Journal of Mineralogical and Petrological Sciences,2005,100(3):91.
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[10]Nassau K,Bohren C F.The physics and chemistry of color[M].New York:John Wiley&Sons,1983:276-280.
[2]Rondeau B,Fritsch E,Mazzero F,et al.Play-of-color opal from Wegel Tena,Wollo Province,Ethiopia[J].Gems&Gemology,2010,46(2):90-105.
[3]陈建.埃塞俄比亚欧泊矿地质特征研究[J].河南科技,2015(9):149-151.
[4]Rondeau B,Gauthier J P,Mazzero F,et al.On the origin of digit patterns in gem opal[J].Gem&Gemology,2013,49(3):138-146.
[5]罗洁,刘喜锋,剡晓旭.澳大利亚、埃塞俄比亚欧泊的对比研究[J].超硬材料工程,2016,28(6):50-57.
[6]Ostrooumov M.Raman,infrared and XRD analysis of the instability in volcanic opals from Mexico[J].Spectrochimica Acta Part A Molecular&Biomolecular Spectroscopy,2007,68(4):1 070-1 076.
[7]任慧珍,李立平.埃塞俄比亚欧泊的成分特征分析[J].宝石和宝石学杂志,2015,17(4):23-28.
[8]Kihara K,Hirose T,Shinoda K.Raman spectra,normal modes and disorder in monoclinic tridymite and its higher temperature orthorhombic modification[J].Journal of Mineralogical and Petrological Sciences,2005,100(3):91.
[9]彭艳菊.晕彩拉长石的成分和结构特征研究[D].北京:中国地质大学,2008.
[10]Nassau K,Bohren C F.The physics and chemistry of color[M].New York:John Wiley&Sons,1983:276-280.