Gemmological Characteristics and Identification of a Kind of Dyed Red Coral Imitation

Through the normal gemmological examination and tested by using X-ray powder diffraction analysis, and infrared spectrum analysis, the results indicate that the gemmological characteristics of dyed red coral imitations are very similar to those of the natural ones. The rough material is a sort of Isis reticulate, which is a kind of reef coral. It is composed of calcite-type high-Mg calcium carbonate. Through the electronic spray ionization-mass spectrometry analysis, the results show that there are two categories of the organic dyed materials, one used earlier is the organic substance with the FM of 728, which can be used as a feature to identify the dyed red coral imitation, and the other used later is a mixed material of a series of organic substance with FM of 312.8, 326.9, and 340.9, just lacking of a -CH₂- between them, which is very similar to that of the organic substances in the natural red coral. Therefore, it is more difficult to accurately distinguish the newest-dyed ones from the natural red corals.