新疆和田“青花玉”仔料的宝石学特征研究

Gemmological Characteristic of "Qinghua" Nephrite from Hetian, Xinjiang

  • 摘要: 近年来,“青花玉”作为和田玉的一个独特品种,虽然未被划入和田玉颜色标样,但该名称在市场实际交易中依然常用,因此研究“青花玉”的宝石学特征,完善其质量评估体系,对提高其市场认知度有着积极意义。本文以新疆和田“青花玉”仔料为研究对象,主要分析其产状、结构、化学成分、显微特征及品质鉴定等方面内容,尝试对其品种进行分类。通过常规宝石学特征观察、偏光显微镜,红外光谱和显微激光拉曼光谱、X射线粉末衍射、扫描电子显微镜及电子探针等测试方法对研究样品进行分析,结果显示,新疆和田“青花玉”仔料的化学成分中Mg/(Fe+Mg)比大于0.9,主要矿物为透闪石。除致色矿物石墨外,还含有白云石、透辉石、绿泥石等副矿物。其形成属中酸性侵入体(岩浆期后溶液)与镁质白云大理岩接触交代成因。

     

    Abstract: As a unique variety of nephrite, although black nephrite ("Qinghua")has not been classified into the mainstream colour variety of nephrite, with the depletion of nephrite mineral resources in recent years, it has gradually attracted people's attention. Therefore, studying the gemmological and mineralogical characteristics of Hetian black nephrites and improving their quality evaluation system have positive significance for improving market awareness.This paper took Hetian black nephrite ("Qinghua") as the research objects, and the samples are from Hetian district, Xinjiang in China. It mainly analyzed the production, structure, chemical composition, microscopic characteristics and quality identification, and try to classify its varieties. It can be determined as Hetian black nephrite by conventional gemmological observation and polarizing microscopy, and then by infrared and microscopic laser Raman spectroscopy, electron probe analysis (EPMA), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). EPMA chemical composition analysis shows black nephrite has a ratio of Mg/(Mg+Fe) being more than 0.90 and the main mineral is tremolite. In addition to the colored mineral graphite, Hetian black nephrite sample also contains minor minerals such as dolomite, diopside and chlorite, etc. Its formation condition belongs to contact metasomatic genesis caused by intermediate-acidic intrusive mass (post-magma solution) and magnesite dolomite marble.

     

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