Identification of Turquoise and Treated Turquoise

Turquoise is one of the four most famous jade in China.Due to its scarcity, quality, and its beautiful appearance, turquoise has been popular with people.In recent years, resource exploitation has made beautiful and good quality turquoise less and less.Therefore, a lot of treated turquoise and imitations appeared on the market.We chose natural turquoise, polymer impregnated turquoise and Zachery treated turquoise as the research objects.We conducted the basic gemmological tests, infrared spectral analysis and laser micro-Raman spectroscopy and X-ray fluorescence spectrometry on these test objects.It is concluded that natural turquoise appears as bright sky blue, green with light oily-vitreous luster, and polymer impregnated turquoise appears as dull colour with weak vitreous-waxy luster, and sometimes one can see polymer residue or polymer enrichment on the surface.Additionally, the density and refractive index of polymer impregnated turquoise is lower than natural turquoise, and the impregnated turquoise appeared with weak to strong blue-white fluorescence.We found that Zachery treated turquoise showed microscopic cracks on both sides of the colour concentration, with the same density, refractive index as natural turquoise.Impregnated turquoise showed infrared spectral characteristics of polymer:ν(as)(CH₂) asymmetric stretching vibration band at 2 920cm^-1, ν_s(CH₂) symmetric stretching vibration band at 2 850cm^-1, and ν(as)(CH₃) asymmetric stretching vibration band at 2 960cm^-1 and infrared absorption band at 1 733cm^-1 caused by ν(C=O) stretching vibration can be used for identification.According to laser Raman spectra, the weak spectrum peaks at 1 455, 1 453cm^-1 of CH₂bending vibration can be used to identify polymer impregnation processed turquoise.X-ray fluorescence spectroscopy showed K element content of Zachery treated turquoise can reach 4.4%.