Spectral Identification Characteristics of Superficial-layer Dyed Golden Seawater Cultured Pearls

The dyestuff types of dyed golden seawater cultured pearls in the jewelry market are still unknown at present,which makes its identification more difficult.The superficiallayer dyed golden seawater cultured pearls are studied by UV-Vis spectrophotometer,Raman microspectrometer,and gem microscope.The results show that the section characteristic of superficial-layer dyed golden seawater cultured pearls are similar to those of golden seawater pearls,whose colour is getting lighter from inside to outside(orange to yellow to faint yellow)and concentric nacreous layers are different from those of traditional dyed golden seawater cultured pearls.The phenomenon of dye enrichment only appears in tiny blemish and no dye enrichment on the surface nacreous layers in superficial-layer dyed golden seawater cultured pearl samples,and their surfaces become faint yellow after repolishing.The diagnostic absorption peak at 398nm in UV-Vis spectrum related to the artificial dyeing agent is only found in the superficial-layer dyed golden seawater cultured pearl samples,and not found in the repolishing facet,section or golden seawater cultured pearls.Raman spectra of superficial-layer dyed golden seawater cultured pearls are the same as those of the golden seawater cultured pearl.Compared with the traditional dyed golden seawater cultured pearl with strong fluorescence background in Raman spectra,the superficial-layer dyed golden seawater cultured pearls do not have strong fluorescence background,whose artificial dyeing agent is too little to cause obvious fluorescence background in Raman spectra.It can't be used to judge the pearl dyed according to the fluorescence background.