Study on Gemmological Characteristics of Rubies from Yuanjiang, Yunnan Province

The gemmological characteristics of rubies from Yuanjiang, Yunnan Province, are analysed by using the conventional gemmological methods and the modern instruments of EMPA, scanning electron microscope, electron paramagnetic resonance, infrared Fourier transform spectroscope and laser Raman spectrometer. The results indicate that the rubies from Yuanjiang have various colour, well-developed partings, a great number of inclusions and surface contaminations. The colour of ruby is caused by Cr. With the increasing of Cr content, the red colour deepens, and the refractive index turns higher. There are 2 or 3 Raman absorption peaks in the range of 200~1 200 cm^-1. In addition to the absorption peaks of 2 110, 1 980 cm^-1, there are three diagnostic absorption peaks of Al₂O₃ at 381, 420, 647 cm^-1 in IR.