Chemical Composition and Spectral Characteristic of Blue Tourmaline from Yunnan Province, China

Nujiang area of Yunnan Province is a rich mining area in China. Since the discovery of Yunnan tourmaline mine in 1980, it is still being mined today, and there has been little comprehensive gemmological researches on it. 9 pieces of blue tourmaline samples from Fugong and Gongshan areas, Yunnan Province, China, have been tested by laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and the contents of main and trace elements of the tested samples were compared with several reported samples of blue tourmalines from other origins. The results indicated that there are tubular and gas-liquid two-phase inclusions in the interior of the blue tourmaline samples by microscopic observation. Raman spectra showed that there is structural water in blue tourmaline samples, and the influence of metal cation content such as Fe element on Raman spectra was pointed out. Based on the characteristic peaks at 4 339 cm^-1 and 4 600 cm^-1, the relationship between element content and absorption peak intensity of blue tourmaline from Yunnan was deduced by infrared spectroscopy. Ultraviolet-Visible absorption spectrum analysis showed that the blue tourmaline samples from Yunnan were caused by valence transition of Fe²⁺-Fe³⁺ and charge transfer of Mn²⁺-Ti⁴⁺. In summary, in view of tourmaline crystal quality and colour, Yunnan, China, is a high-quality source of tourmaline.