Gemmological Characteristic of Yellow Diamond with 480 nm Absorption Peak of UV-Visible Spectrum

In recent years, more and more yellow diamonds have been sent to our center for identification. There are many causes of formation of yellow diamonds, in addition to the yellow diamonds related to the N3 center, yellow diamonds with absorption peak at 480 nm in UV-Vis absorption spectrum are also often encountered in the laboratory. Therefore, it is particularly important to have a in-depth study of the various causes of colouration of yellow diamonds for identification. In this paper, ultraviolet visible optical fiber spectrometer, infrared spectrometer, laser confocal Raman spectrometer and DiamondView^TM were used to systematically study the relatively rare yellow diamonds with 480 nm absorption peak in UV-Vis spectrum. The results show that the UV-Vis spectra, infrared spectra and Raman spectra of the yellow diamonds with 480 nm absorption peak in UV-Vis spectra have high similarity: They are all type Ia diamonds, in addition to N element, they also contain H, Ni elements; They all have dislocations caused by plastic deformation. The analysis of these characteristics show that these diamonds are natural and have not been undergone heat teatment. The author speculates that the cause of the colour of these yellow diamonds may be related to Ni element and the vacancy produced by plastic deformation.