“非洲独龙玉”的矿物成分及谱学特征

doi:10.3964/j.issn.1000-0593(2024)06-1676-08

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摘要： “非洲独龙玉”是近年来滇西珠宝市场上涌现的新兴玉石品种。其鲜艳绿色呈脉状和团絮状分布于无色至灰白色基体上，局部存在红褐色。品质优于云南怒江州“独龙玉”，市场前景引起业界广泛关注，但其宝石学特征及矿物种属尚不清楚。运用红外光谱仪、拉曼光谱仪、X射线粉晶衍射仪、扫描电子显微镜及能谱、X射线荧光光谱仪、紫外-可见光谱仪等测试方法对其矿物组成及结构特征、化学成分、谱学特征及颜色成因等进行了研究。红外光谱测试表明该玉石的绿色部分显示白云母与石英的红外特征混合谱，其中3 623、694、1 080和1 619 cm^-1处特征吸收峰指示白云母。拉曼光谱测试显示玉石基体部分在204、262、355、395和463 cm^-1处具α-石英特征峰，绿色部分在261、395、694、3 623 cm^-1处具白云母特征峰，表面金属光泽矿物在343、379和437 cm^-1处具黄铁矿特征峰，局部浸染状橙黄-红褐色矿物在224、295、409、493和610 cm^-1处具赤铁矿特征峰。X射线粉晶衍射测试在3.48、2.98、2.56 Å处特征衍射峰指示为2M₁型白云母。扫描电子显微镜及能谱面扫描显示白云母呈纤柱状、鳞片状集合体，单颗粒长约25～40 μm，宽约2～4 μm；少量杂质矿物辉砷镍矿呈近似立方体晶形，粒径约为10～15 μm，由黄铁矿蚀变作用形成，其中Fe、Co部分类质同像替代Ni，As含量高于S，指示为高温热液矿床成因。综合化学成分及紫外-可见光谱特征表明，致色矿物白云母含Ba、Cr，不含Fe，其中Cr为致色元素。除颜色特征外，利用多种谱学的方法揭示了“非洲独龙玉”与云南怒江“独龙玉”在杂质矿物、化学成分及致色元素方面的差异，可作为区分二者的有效证据，同时丰富了天然绿色石英质玉的成分信息和谱学特征数据，亦为进一步做“非洲独龙玉”的产地溯源及成矿地质条件背景研究奠定了理论基础。

关键词：“非洲独龙玉”；矿物组成；辉砷镍矿；颜色成因；谱学特征

Abstract：In recent years, a novel variety of jade known as “African Dulong Jade” has emerged in the jewelry market of Western Yunnan. It possesses a distinctive, vibrant green hue adorned with intricate veins and feathery patterns, juxtaposed against a colorless greyish-white matrix, occasionally tinged with reddish-brown tones. Notably, its quality surpasses that of the “Dulong Jade” found in the Nujiang Prefecture Yunnan Province, exhibiting promising market expansion prospects.However, the gemological characteristics and mineral species of this jade remain mysterious.To shed light on this subject, this research explores the mineral composition, structural characteristics, chemical components, spectral attributes, and the origin of its captivating color. Employing advanced analytical instruments such as the Infrared spectrometer, Raman spectrometer, X-ray powder diffractometer, Scanning electron microscope, Energy dispersive spectroscopy, X-ray fluorescence spectrometer, and Ultraviolet-visible spectrometer, the study delves into a comprehensive investigation.The infrared spectrum examination reveals that the green portion of the jade exhibits mixed infrared spectrum characteristics akin to both muscovite and quartz. Notably, infrared absorption peaks at 3 623, 1 080, 694 and 1 619 cm^-1 signify the presence of muscovite. Raman spectra demonstrate that the matrix component of the jade corresponds to α-quartz, as evidenced by characteristic peaks observed at 204, 262, 355, 395 and 463 cm^-1. Conversely, the green section of the jade displays muscovite characteristics with peaks highlighting at 261, 395, 694 and 3 623 cm^-1. Furthermore, the metallic luster observed on the surface of the mineral signifies the presence of pyrite, with characteristic peaks at 343, 379, and 437 cm^-1. Locally disseminated orange-yellow to reddish-brown minerals are identified as hematite, exhibiting characteristic peaks at 224, 295, 409, 493 and 610 cm^-1. X-ray powder diffraction analysis confirms the existence of 2M1 muscovite with discernible diffraction peaks observed at 3.489, 2.981 and 2.563 Å. Insights obtained from scanning electron microscope and energy spectrum scanning elucidate that muscovite manifests as columnar and scale-like aggregates, featuring individual particle lengths ranging from 25 to 40 μm and widths of 2 to 4 μm. Additionally, gersdorffite, an impurity mineral, exhibits minimal content and particle sizes of approximately 10 to 15 μm. Within gersdorffite, iron (Fe) and cobalt (Co) elements partially replace nickel (Ni) through isomorphism. Moreover, the greater concentration of arsenic (As) compared to sulfur (S) suggests a high-temperature hydrothermal deposition origin.Through chemical composition analysis and ultraviolet-visible spectra examination, it is ascertained that the chromogenic mineral muscovite contains barium (Ba) and chromium (Cr), while iron (Fe) is lacking in the quartz matrix. Furthermore, the content of Ba exceeds that of Cr, which acts as the chromic element within muscovite. Beyond color characteristics, this study reveals distinguishing chromogenic elements, chemical composition, and impurity minerals between “African Dulong Jade” and “Dulong Jade” from NujiangPrefecture Yunnan Province using various spectral techniques.These findings serve as compelling evidence for differentiating the two “Dulong Jade” types and contribute to an enhanced understanding of the component information and spectral characteristics of naturally occurring green quartzite jades. Consequently, it establishes a foundation for future inquiries into the metallogenesis geological background and geographical origin tractability of “African Dulong Jade”.

Key words：“African Dulong Jade”;Mineral compositon;Gersdorffite;Color origin;Spectroscopic characteristic

收稿日期: 2023-04-22 修订日期: 2023-11-23

中图分类号:

P575

基金资助: 国家自然科学基金项目（42072252），云南省教育厅科学研究基金项目（2023J1710）资助

作者简介: 余炼钢，1980年生，德宏师范高等专科学校副教授 e-mail: ylg2004260@163.com

引用本文:

余炼钢，郑金宇. “非洲独龙玉”的矿物成分及谱学特征[J]. 光谱学与光谱分析, 2024, 44(06): 1676-1683.
YU Lian-gang, ZHENG Jin-yu. Study on Mineral Composition and Spectroscopy Characteristics of “African Dulong Jade”. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(06): 1676-1683.

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https://www.gpxygpfx.com/CN/10.3964/j.issn.1000-0593(2024)06-1676-08 或 https://www.gpxygpfx.com/CN/Y2024/V44/I06/1676

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