Identification Characteristics of Composite Coral

Recently，the quantity of coral products with large size is increasing in the jewelry market.In fact，these large size coral products are mainly suspicious composite corals，which are combined by coral fragments and cements.There is little systematic summary on the identification characteristics for these corals.In this paper，the identification characteristics and testing methods are summarized and discussed relying on long－term experiences and researches at gemstone testing center.It is found that there are two types of the composite corals.The typeⅠis composed of coral fragments and cements，while typeⅡconsists of coral fragments，artificial matrix materials and cements.Magnification and ultraviolet fluorescence of the composite corals were observed.The appearance and luminescence characteristics were distinctive different between cements，matrix materials and the main part of coral products.By using infrared spectrometer to confirm the compositions of cementing material，it is found that they are mainly methyl methacrylate and epoxy resin and the compositions of some of the matrix materials detected from certain composite corals are mainly alkyd resin（mixed with carbonate material powder）and ethyl cyanoacrylate.Comprehensive applications of magnification and ultraviolet fluorescence observation with infrared spectrometer would be used to identify composite coral quickly，accurately and effectively.