Identification Features of Black Coral,Golden Coral and Cirrhipathes

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.