合成扩散星光刚玉的物理性质及成因探讨

Physical Properties and Origins of Synthetic and Diffused Star Corundum

通过常规的宝石学测试方法、电子探针分析及紫外 -可见光谱分析等测试 ,详细研究了 3块待测样品的化学成分和物理性质 ,并将其与天然刚玉及合成星光刚玉进行了对比研究 .3块待测样品的颜色分别为橙红色、褐红色及紫红色 ,透明度较高 ,其中橙红色的为近透明 ,另外 2粒为半透明 .强光下发现样品的表面有一层云雾状的物质 .星光浮于表面 ,且较为发散、弯曲 .星光相交处可见宝光 .显微镜下观察发现 ,3块样品的表面均有较多的凹坑 ,其中2块近表面可见隐约的丝状包裹体 ,但定向性较差 ;1块似有熔融的特征 .这些特征表明 ,这 3块样品中包裹体可能是经过高温处理而成 ,非合成退火所致 .3块样品均可见到较明显的细密的弯曲生长纹 ,表明其为焰熔法合成产物 .电子探针分析结果显示 ,3块样品的致色元素均为铬 ,为红宝石 ;丝状体为钛酸铝 .紫外 -可见光谱测试结果表明 ,其吸收光谱为铬吸收谱 .综合分析所有的特征 ,认为这 3块样品为焰熔法合成红宝石 ,星光的产生是在合成红宝石生成加工后 ,通过扩散作用所形成的丝状钛酸铝对光的反射所致 .

This paper analyzes the chemical composition and physical properties of three star corundum specimens based on routine gemmological tests, electronic probe analysis and ultraviolet-visible spectrum analysis. In addition, the authors analyze the origin of star corundum. The observations show that the tested three specimens appear orange-red, brownish red and mauve and have relatively high transparency. Under strong reflected light, these three specimens exhibit cloudy surface features. The star lines from the surface of the stones are diffused and curved. At the intersection of the star lines, a bright light area can be seen. Through a microscope, these three specimens show well-developed pits and mocks. Two specimens show poorly-defined fibrous aluminum titanate inclusions, but one shows melted surface. All of these features indicate that the fibrous aluminum titanate inclusions seen in these three specimens may be produced by diffusion at a high temperature but annealing after being synthesized. All of these three specimens show obvious closed-arranged curved growth striations, indicating an origin of flame fusion. The electronic probe analysis results, absorption spectrum observations and ultraviolet-visible spectrum analysis give a Cr coloring element for these three specimens. Therefore, these three specimens should be named star ruby, and the color is caused by the synthesis but diffusion origin. However, the asterism is caused by the reflection from fibrous aluminum titanate inclusions produced by diffusion.