云南元江红宝石的矿物宝石学特征及热处理研究

【作者】 业冬；

【导师】 赵昆渝； 祖恩东；

【作者基本信息】 昆明理工大学 ， 材料学， 2007， 硕士

【摘要】 云南元江红宝石发现于20世纪90年代，是目前国内最好的红宝石矿。在世界范围内，有关它的报道和研究很少。本文采用常规的宝石学研究方法以及电子探针、扫描电子显微镜、电子顺磁共振、傅立叶变换红外光谱仪、拉曼光谱仪、紫外可见光分光光度计等现代测试仪器，对元江红宝石的矿物宝石学特征进行了系统的研究，并结合晶体场理论分析元江红宝石的致色机理。结果表明，云南元江红宝石颜色丰富，裂理发育，存在大量包裹体，主要致色离子为Cr。随着Cr含量增高红色逐渐加深，折射率也随之增大。其拉曼光谱在200-1200cm^-1范围内有2—3个拉曼吸收峰，分别位于381，420，647cm^-1处，其中420和647峰属A_1g不可约表示，381峰属E_g不可约表示。红外光谱除2110、1980cm^-1的吸收双峰外，出现3085和3312cm^-1两个氢氧键伸缩振动的特征吸收峰。元江红宝石中的Cr、Fe、Mn主要以Cr³⁺、Fe³⁺、Mn²⁺的形式类质同象替代八面体中的Al³⁺，其颜色主要取决于Cr³⁺的d—d电子跃迁，Fe、Ti离子的电荷转移，Fe³⁺的d—d电子跃迁，Ti³⁺的d—d电子跃迁都起到了一定影响。红色调主要由Cr³⁺的⁴A₂→⁴T₂和⁴A₂→⁴T₁晶体场跃迁引起；紫色调主要是由Fe²⁺+Ti⁴⁺的电荷转移引起的；黄色调主要由Fe³⁺的⁶A₁→⁴A₁+⁴E₁晶体场跃迁引起。论文在矿物宝石学特征研究基础上，对元江红宝石进行了热处理实验。发现在1350—1580℃，助熔剂为Al（OH）₃和无水硼砂的热处理实验中，元江红宝石得到一定的改善，颜色、透明度均有所提高。热处理可以消除红宝石中的紫色调、黄色调及其它杂色调，使得宝石更加鲜艳，荧光性更强；同时加热会使宝石内的包裹体熔融、扩散，助熔剂会使裂隙愈合，从而使红宝石看起来更透明。更多还原

【Abstract】 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.更多还原