UV-Vis Spectral Characteristic and Colour Characterization of Turquoise from Tongling, Anhui Province

In this paper, UV-Vis spectrometer, infrared spectrometer and other methods of gemmological analysis were used to study the micropscopic characteristics, UV-Vis spectra, infrared spectra and colour characterization of the turquoise samples from Tongling, Anhui Province. The results showed that the UV-Vis spectra of the turquoise samples from Tongling reveals ³⁺ absorption at 421, 429 nm, and the wide absorption band of the yellow-green area near the near infrared region is caused by ²⁺. As the main wavelength of the turquoise samples becomes smaller, the wide absorption band caused by ²⁺ moves towards the short wave direction. In addition, the brightness value of the turquoise samples from Tongling is negatively correlated with the chroma value when the main wavelength is similar. The results showed that the turquoise samples from Tongling have the same infrared spectra characteristic as turquoises from the other origins, and there is only a small deviation in a few wavenumbers which indicates that the molecular composition of the turquoise samples from Tongling is the same as turquoises from the other origins.