一种盐源玛瑙仿制品的宝石学及谱学特征

Gemmological and Spectroscopic Characteristics of A Kind of Imitation of Agate from Yanyuan

  • 摘要: 近期,一种盐源玛瑙仿制品(商家称“新矿盐源玛瑙”)在市场上出现,其外观与盐源玛瑙非常相似。为确定其矿物组成、化学成分及谱学特征,采用常规宝石学测试方法、傅里叶变换红外光谱、拉曼光谱、X射线荧光光谱和紫外-可见光谱等测试方法对此类仿制品样品进行了宝石学及谱学特征研究。结果显示,该仿制品样品密度大于2.70 g/cm3,小刀可轻易划动,滴盐酸起泡,结构细腻,内部零散分布着大小不等的黑色点状物;红外光谱和拉曼光谱分析均显示了其具有重晶石、方解石及环氧树脂的特征峰位;X射线荧光光谱分析显示了其主量元素为Ba、Sr、S,与重晶石的主量元素一致;紫外-可见光谱分析认为,其粉红色部位的致色可能与赤铁矿有关,黄绿色部位的致色可能与针铁矿及Cu2+共同作用有关,这与天然盐源玛瑙中粉红色、黄绿色的致色机制相似。综合分析认为,该类“新矿盐源玛瑙”实为重晶石、方解石和环氧树脂的混合物,在日常检测中可以依据常规宝石学特征与盐源玛瑙快速区分,谱学特征可帮助进一步确定该仿制品的矿物组成,且根据GB/T16553-2017《珠宝玉石鉴定》,建议定名为“仿玛瑙”。

     

    Abstract: Recently, a kind of imitation, whose appearance is very similar to that of agate from Yanyuan has appeared in the market. In order to determine its mineral components, chemical compositions and spectral characteristics, the conventional gemmological test methods, Fourier transform infrared spectroscopy(FTIR), Raman spectroscopy, X-ray fluorescence spectroscopy(XRF), ultraviolet-visible spectroscopy(UV-Vis) and other testing methods were used. The results show that the density of the imitation sample is greater than 2.70 g/cm3, and it can be easily scratched by a knife, and blistered by drops of hydrochloric acid. It has a fine structure, and has black dots of varying sizes sporadically distributed inside. Infrared spectra and Raman spectra show that it has the characteristic peaks of barite, calcite and epoxy resin. X-ray fluorescence spectra show that the main elements are Ba, Sr, S, which are consistent with barite. UV-Visible spectra show that the colouration of the pink part may be related to hematite, and the colouration of the yellow-green part may be related to the combined action of goethite and Cu2 +, which is similar to the colouration mechanism of pink and yellow-green colours in natural agate from Yanyuan. Based on the analyses, this kind of "Yanyuan agate" is actually a mixture of barite, calcite and epoxy resin. In daily identification, it can be identified rapidly based on conventional gemmological features, and the spectroscopic features can help to further determine the mineral components of the imitation. According to GB/T 16553-2017 Identification of Jewelry and Jade, it is recommended that the terms "agate imitation" should be used instead.

     

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