Visible Absorption Spectrum Characteristics of Qingu Turquoise from Hubei Province

The visible absorption spectra of Qingu turquoise samples from Hubei Province are mainly tested by USB2000 Fiber Optic Spectrometer.The results show that two particular and wide absorption bands,band a₁ (425~428 nm) and band a₃(693~688 nm),are present in Qingu turquoise samples,and the dominant wavelength and purity of the visible absorption spectrum are corresponding to the colour characteristics.The results of the visible absorption spectra at rising temperatures and differential thermal analysis indicate that the colour characteristics of Qingu turquoise could be related to the iron ion and water content.