翡翠原石皮壳的宝石学特征研究

发布时间：2018-04-30 03:22

本文选题：宝石学特征 + 硬玉　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：自古有言“黄金有价,玉无价。”翡翠在我国的玉文化中占据重要地位,它的颜色丰富,质地温润,且韧性良好,是当之无愧的“玉石之王”。对翡翠风化作用形成皮壳的特征研究有助于判别内部质量状况,前人对其有一定程度的研究,但其形成机理研究还不够深入。本文从广东佛山平洲收集了不同颜色皮壳的翡翠原石,对其进行宝石学常规测试,显微镜下观察,电子探针、X射线粉晶衍射和红外光谱和紫外-可见光光谱等测试实验,对次生作用下翡翠的矿物组成及其化学成分特征,结构特征和谱学特征等方面进行研究,探讨不同皮壳的致色原因及结构的变化。电子探针测试表明样品的主要矿物有硬玉,次要矿物有浅闪石、蓝闪石等闪石族矿物。皮壳处的矿物颗粒并未改变成分,内部矿物为硬玉的皮壳也为硬玉,而充填于颗粒间隙的次生矿物可能多为褐铁矿、赤铁矿和绿泥石等粘土矿物,且绿泥石中主要致色元素为Fe2+。内部正绿色翡翠的皮壳处虽然已经风化为褐红色等,但皮壳中硬玉仍含有0.1-0.2%的Cr2O3,内部为较纯的硬玉矿物。偏光显微镜下观察显示,翡翠皮壳的结构与内部特征具有相关性。所选取的大多数翡翠样品皮壳与内部矿物颗粒都为硬玉,皮壳处结构疏松,颗粒间隙较大,颗粒间隙充填有暗色隐晶质-微晶质矿物,部分样品黑色皮壳矿物颗粒表现为蚀变现象。次生油青种翡翠中可见呈细微的网脉状结构及交代残余结构,为暗色隐晶质矿物可能以充填或交代的形式存在于翡翠中而致色。X射线粉晶衍射测试显示黑乌砂皮处的矿物除硬玉外,还有有绿泥石等次生矿物;红外光谱测试图谱显示,黑乌砂皮翡翠和部分黄砂皮翡翠的皮壳颜色3500cm-1处有较宽且平缓的吸收峰,可能指示次生作用为主要致色原因;紫外-可见光光谱显示正绿色翡翠的绿色部分主要为Cr3+致色,浅绿色的翡翠同时具有铁和铬的吸收峰,翠绿色的翡翠只有明显的铬吸收峰。由于三价铁对翡翠颜色贡献不大,结合探针数据,可推断翡翠浅绿色主要为Cr3+致色,翠绿色主要为Cr3+和Fe2+共同致色。
[Abstract]:Since ancient times, there has been a saying, "Gold has price, jade is priceless." Jade occupies an important position in the jade culture of our country, its color is rich, texture is warm and moist, and toughness is good, it is worthy of "King of Jade". The study on the characteristics of the weathering of jadeite jade is helpful to distinguish the internal quality, but the research on the formation mechanism of jadeite is not deep enough. In this paper, the jadeite of different color shell has been collected from Pingzhou, Foshan, Guangdong Province, and has been tested by conventional gemstone test, microscope observation, electron probe X-ray powder diffraction, infrared spectrum and UV-Vis spectrum, etc. The mineral composition, chemical composition, structural and spectral characteristics of jadeite jade under secondary action were studied. The electron probe test shows that the main minerals of the samples are jadeite, the minor minerals are amphibole, blue amphibole and other amphibole minerals. The mineral particles in the crust have not changed the composition, and the crust with the inner mineral is jadeite, while the secondary minerals filled in the intergranular space may be mainly limonite, hematite and chlorite, etc. Clay minerals, such as limonite, hematite, chlorite, etc. The main chromogenic element in chlorite is Fe2. Although the crust of the jadeite is weathered to brownish red, the jadeite still contains 0.1-0.2% Cr _ 2O _ 3 and is a pure jadeite mineral. Under polarizing microscope, the structure of jadeite shell is correlated with its internal characteristics. Most of the jadeite samples' crust and inner mineral particles are jadeite, the structure of the shell is loose, the grain gap is large, and the granular gap is filled with dark cryptic and microcrystalline minerals. Some of the black crust mineral particles are altered. In the secondary oil green jadeite, the net vein structure and the metasomatic residual structure can be seen. The results of X-ray powder diffraction analysis showed that the minerals in the black sand skin had secondary minerals, such as chlorite, in addition to jadeite, and the infrared spectra showed that, in addition to jadeite, there were some secondary minerals, such as chlorite, in the form of filling or metasomatism. There is a wide and gentle absorption peak at the 3500cm-1 of the shell color of the jadeite and part of the yellow jadeite jade, which may indicate that the secondary action is the main cause of chromogenic effect, and the UV-Vis spectrum shows that the green part of the emerald is mainly Cr3 chromogenic. The light green jadeite has the absorption peak of iron and chromium at the same time, and the emerald with emerald green has only the obvious absorption peak of chromium. Due to the little contribution of trivalent iron to the color of jadeite, it can be inferred that the light green of jadeite is mainly Cr3 chromogenic, the emerald green is mainly caused by Cr3 and Fe2, combined with the probe data.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P619.28

【参考文献】