Mineralogical Characteristic of Black Quartzose Jade from Linwu, Hunan Province
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摘要: 近年来, 石英质玉石逐渐进入市场并为大众所接受，湖南临武县通天山新近发现一种商业名称为"通天墨玉"的灰黑色-黑色石英质玉，成品整体呈现出微弱的胶质感。结合前人对于石英质玉石的研究，采用常规宝石学测试、偏光显微镜、X射线粉末衍射、电子探针、红外光谱、激光拉曼光谱以及紫外-可见分光光度计对该地区样品的矿物组成、化学成分、谱学特征等进行测试分析，并进一步探讨其成矿机理与颜色成因。结果表明，湖南临武地区石英质玉多为隐晶质-细粒结构，偏光显微镜下可见变晶、变余结构。成分除无机矿物外，含有机碳，其中主要组成矿物石英约占50%，脆性矿物长石、白云母等约占30%，黏土矿物含量约为10%，另含有少量红柱石、铁铝榴石以及黄铁矿等铁质矿物。综合结构、成分分析的结果，推测其由硅质页岩经浅变质作用而形成。红外光谱、拉曼光谱均可见石英的特征吸收峰，Si-O键吸收分裂明显表明石英的结晶程度较高；紫外-可见分光光度计测试样品可见波长450~500 nm间Fe的特征吸收，结合薄片中有机碳的充填程度、拉曼光谱及紫外色品图颜色测量的结果，推测样品主要为碳质杂质致色。Abstract: In recent years, quartzose jade has gradually entered the market and been accepted by the public. A new kind of gray-black or black quartzose jade named "Tongtianmoyu" has been found in Linwu, Hunan Province. Mineral components and chemical compositions were analyzed by conventional gemmological instruments, polarizing microscope, X-ray powder diffraction(XRD) spectrometer, and electron probe micro-analyzer(EPMA). Spectroscopy characteristics were analyzed by Fourier transform infrared(FTIR) spectrometer, Raman spectrometer, and ultraviolet-visible (UV-Vis) spectrometer. The results turn out that the main structure of the quartzose jade is cryptocrystalline-fine grain structure. Further, crystalloblastic structure and palimpsest structure were observed under the polarizing microscope. In addition to organic carbon, it contains inorganic minerals, of which quartz accounts for about 50%, feldspar and muscovite account for about 30%, clay minerals account for about 10%, and a small amount of andalusite, almandite, pyrite and other Fe-minerals. Combining the results of structure and composition analyses, it is inferred that the quartzose jade was formed by siliceous shale under an epimetamorphism process. The characteristic absorption peaks of quartz can be seen in the FTIR and Raman spectra, and the Si-O bond absorption and division indicate the high crystallization degree of quartz. Characteristic absorption of Fe at visible wavelength of 450-500 nm was measured by UV-Vis spectrometer. Based on the results of filling degree of organic carbon, Raman spectrum and UV chromatogram, it can be inferred that the colour of the samples is mainly caused by carbon impurities.
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Keywords:
- quartzose jade /
- mineralogical characteristic /
- genesis /
- colouring mechanism /
- Hunan Province
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图 2 湖南临武石英质玉的结构a，d.大量石英颗粒呈斑团状分布于碳质基质中；b，e.大量石英颗粒呈斑团状分布于黑云母、金云母混合基质中；c，f.放大可见大量它形石英及片状云母矿物颗粒(a，b.单偏光2.5×；c.单偏光10×；d，e.正交偏光2.5×；f.正交偏光10×)Figure 2. Structures of quartzose jade from Linwu, Hunan Province![]()
图 3 湖南临武石英质玉的X射线衍射图谱Q-石英；M-白云母；F-长石；G-石榴石；A-红柱石；P-黄铁矿；I-钛铁矿；L-磷灰石；C-绿泥石Figure 3. XRD patterns of quartzose jades from Linwu, Hunan Province![]()
图 4 湖南临武石英质玉的红外光谱注：1 200~1 000 cm-1处呈现肩峰吸收样式，800、700、698及513 cm-1附近石英特征吸收峰Figure 4. FTIR spectra of quartzose jade from Linwu, Hunan Province![]()
图 5 湖南临武石英质玉的拉曼光谱注：465、393、1 079 cm-1为石英特征吸收峰；681 cm-1白云母吸收峰；920 cm-1红柱石吸收峰；1 300~1 200 cm-1间有机碳吸收峰；1 582 cm-1处石墨特征吸收峰Figure 5. Raman spectra of quartzose jade from Linwu, Hunan Province -
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图 2 湖南临武石英质玉的结构
a，d.大量石英颗粒呈斑团状分布于碳质基质中；b，e.大量石英颗粒呈斑团状分布于黑云母、金云母混合基质中；c，f.放大可见大量它形石英及片状云母矿物颗粒(a，b.单偏光2.5×；c.单偏光10×；d，e.正交偏光2.5×；f.正交偏光10×)
Figure 2. Structures of quartzose jade from Linwu, Hunan Province
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图 3 湖南临武石英质玉的X射线衍射图谱
Q-石英；M-白云母；F-长石；G-石榴石；A-红柱石；P-黄铁矿；I-钛铁矿；L-磷灰石；C-绿泥石
Figure 3. XRD patterns of quartzose jades from Linwu, Hunan Province
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图 4 湖南临武石英质玉的红外光谱
注：1 200~1 000 cm-1处呈现肩峰吸收样式，800、700、698及513 cm-1附近石英特征吸收峰
Figure 4. FTIR spectra of quartzose jade from Linwu, Hunan Province
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