Yunnan Yuanjiang Ruby ​​mineral Gemological Characteristics And Heat Treatment Studies

Yuanjiang ruby which was found in Yunnan province in 1990 is the best quality ruby in China. The reports and studies about the rubies are very rare. The dissertation deals with the gemology and relative spectroscopy of these rubies by using the conventional gemological 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 Yuanjiang ruby have variously color, well-developed partings, a great number of inclusions and surface contaminations. The color of ruby is caused by the color-causing element chromium. With increasing Cr content, the red color deepens, and the refractive index turns higher. There are 2 or 3 Raman absorption peaks in the range of 200～1200cm^-1.The peaks of 420,647cm^-1 belong to A_<sub>1g irreducible representation, the peak of 381cm^-1 belong to E_g irreducible representation. In addition to the absorption of 2110cm-l,1980cm-l peaks ,there are two diagnostic absorption peaks of 3085 and 3312cm^-1 in IR. EPR was mainly caused by inclusion irons such as Cr, Fe and Mn. Then Cr³⁺, Fe³⁺, Mn²⁺ which replaced Al³⁺ in the internal structure were the major cause of coloration of Yuanjiang ruby. The red color of Yuanjiang ruby mainly depended on the d-d leap of Cr³⁺. The purple part of Yuanjiang ruby is mostly colored by transferring leap of Fe²⁺+Ti⁴⁺-Fe³⁺+Ti³⁺, the yellow part is chiefly caused by the d-d leap of Fe³⁺.Based on the study of gemology and relative spectroscope, heat treatment of Yuanjiang ruby to enhance color and clarity has been done. Fluxes and additives used in the treatment are Al(0H)₃ and anhydrous borax. It was found that by heating Yuanjiang ruby in oxygen gas atmosphere between 1350℃ to 1580℃ could lead to a more perfect ruby.