黑珊瑚、金珊瑚及海藤的鉴别特征

Identification Features of Black Coral,Golden Coral and Cirrhipathes

  • 摘要: 黑珊瑚、金珊瑚和海藤都是角质珊瑚的主要品种,由于黑珊瑚和金珊瑚的产量稀少,在市场上常用海藤作为其替代品。为查明海藤、漂白海藤与黑珊瑚、金珊瑚在生物学分类中的种属及其结构和成分上的鉴别特征,自专门从事珊瑚贸易的台湾珠宝商处收集了海藤、漂白海藤、金珊瑚、黑珊瑚样品,对比分析其结构和成分。查明了这三类品种在生物学上的分类,黑珊瑚和金珊瑚为分枝状结构,而海藤则无分支。常规宝石学测试发现,黑珊瑚和海藤具有相近的外观和物理性质,金珊瑚的折射率较低且相对密度较高,漂白海藤的外观与金珊瑚的相似,但其折射率和相对密度与金珊瑚的都略有偏差。扫描电子显微镜观察发现,在横截面上,三类样品均具有同心层结构,但海藤的同心层结构较疏松,并伴有放射状纹理;黑珊瑚的侧表面光滑,有些黑珊瑚表面有丘疹,金珊瑚侧表面有平行纵纹,有时有晕彩,海藤侧表面有明显的丘疹,且丘疹是形成放射状纹理的原因。红外光谱、X射线粉末衍射及拉曼光谱的测试结果表明,黑珊瑚和海藤的化学成分以有机组分为主,海藤及漂白海藤含有磷的化合物,金珊瑚含有较多的文石和方解石,也含有一定量的有机组分。外观、结构特征、折射率和相对密度以及红外光谱特征可作为区分黑珊瑚和海藤,金珊瑚与漂白海藤的依据。

     

    Abstract: Black coral,golden coral and Cirrhipathes are three main varieties of horniness coral.Because of limited production of black coral and golden coral,Cirrhipathes is often used as the substitutes of these corals.Firstly,the authors classified black coral,golden coral and Cirrhipathes in biological order,then adopted conventional gemmological testing methods.And the results of RI,relative density,and ultraviolet fluorescence show that the black coral possesses similar appearance and physical properties with Cirrhipathes.Golden coral has lower RI and higher relative density than bleached Cirrhipathes.Secondly,scanning electron microscopy analysis of the black coral,golden coral and Cirrhipathes,reveals that all the samples show concentric structure on cross sections.Black coral and golden coral have branching structure,and more compact structure on cross section.The surface of black coral is smooth though some black coral have pimples,and the surface of golden coral shows parallel lines,sometimes iridescence.Cirrhipathes has no branching structure,and it shows concentric structure and radial grains on cross section,and pimples on surfaces.The pimple is caused by the radial grains.Finally,infrared spectroscopy,X-powder diffraction spectrometer and Raman spectrometer are applied to analyse chemical compositions.The black coral and Cirrhipathes mainly consist of organic componene.Cirrhipathes and bleached Cirrhipathes contain phosphorus compounds,but the golden coral contains aragonite and calcite,including organic substance.Therefore,the appearance,RI,relative density,and the characteristics of infrared spectra can be used to distinguish black coral from Cirrhipathes,and golden coral from bleached Cirrhipathes.

     

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