Gemmological Characteristic of Ruby from Baicheng, Xinjiang

In this paper, we researched the gemmological characteristics of ruby samples produced in Baicheng, Xinjiang by using geological and gemmological methods, polarizing microscope, electron microprobe, Fourier transform infrared spectroscopy and UV-Vis absorption spectroscopy. The ruby produced in mica marble belongs to typical marble-type ruby deposits.The ruby assumes a pink to rose red to red colour, and the colour thickens with the increase of Cr content. All rubies have strong red fluorescence under long-wave ultraviolet light. The main mineral inclusions are calcite, pyrite, sphalerite, diaspore, acicular and veil-like inclusions. The functional region showed 1 990, 2 121, 2 929 cm^-1 diaspore characteristic infrared absorption peaks. In the UV-Vis absorption spectra, the ruby show typical 693.9 nm strong fluorescence band of Cr. The content range of Cr₂O₃ in ruby is 0.11%~0.62%, while those of FeO_T and TiO₂ are extremely low. Compared with the famous ruby origins around the world, the ruby from Baicheng has high Cr content, low Fe and Ti content. Some ruby samples have bright colour and show strong fluorescence characteristics of "pigeon's blood" ruby.