市场常见天然及染色火欧泊的颜色特征及鉴定特征

Study on Colour and Identification Characteristics of Natural and Dyed Fire Opal in the Market

火欧泊作为名贵的欧泊品种在市场上一直广受喜爱。火欧泊的颜色成因及鉴定一直是检测中的难题。随着市场对于染色火欧泊辨别的需求变得越来越迫切,具有一定的研究意义。选取市场上常见的天然及染色火欧泊样品作为研究对象,通过常规宝石学测试、傅里叶变换红外光谱仪、DiamondView^(TM)、光致发光光谱、紫外-可见光谱和拉曼光谱等测试仪器分析了市场上常见的火欧泊品种、各产地火欧泊样品的宝石学特征及鉴定方法,以期探索通过实验室常规技术手段区分火欧泊体色天然成因及染色的方法。结果发现,绝大部分天然火欧泊均具有不同程度的颜色分区及色脉,染色样品无此现象;在DiamondView^(TM)下,天然和染色火欧泊样品的荧光图像具有显著差异;红外光谱和拉曼光谱可以辅助区分产地,非洲染色欧泊样品的拉曼光谱可见1200~1600 cm^(-1)范围内的染剂吸收峰;染色与天然火欧泊的PL光谱也显示峰型及峰位差异。染色火欧泊样品与天然火欧泊样品在紫外-可见光谱中并无明显区别。外观特征、谱学特征及发光特征的综合分析,可应用于实际检测区分染色火欧泊与天然火欧泊。

Fire opal as a rare opal variety in the market has been widely loved.The cause and identification of the colour of fire opal has always been a difficult problem in testing.As the market demand for dyed fire opal identification becomes more and more urgent,it has a certain degree of significance in research and application.This article selected the common natural and dyed fire opals in the market as the research objects.Conventional gemmological tests,microscopic observations,Fourier infrared spectrometer,DiamondView^(TM),photoluminescence spectroscopy,ultraviolet-visible spectroscopy and Raman spectroscopy tests were done to analyze the gemmological characteristics and identification methods of common fire opals from different areas on the market,which may provide clues to explore the method of distinguishing natural body colour fire opal and dyed fire opal by conventional laboratory technique.Research results showed that most natural fire opals are uneven in colour to some extent,while dyed samples not.There are some significant differences in the fluorescence images of natural and dyed fire opal under DiamondView^(TM).Infrared and Raman spectroscopy can assist in distinguishing the fire opal origin.Dyed samples from Africa had the dye absorption peaks within the range from 1200 to 1600 cm^(-1).There are also some difference of peak shape and absorption peak between dyed and natural fire opal in PL test.There was no obvious difference between the dyeing fire opal and natural fire opal in UV-Vis spectra.The full contrast of appearance features and the comprehensive analysis of spectral and luminescent characteristics can be used to distinguish the colour origin of the fire opal in practice.