三个产地碧玉的矿物组成及化学组成特征

Mineral Composition and Chemical Composition Characteristics of Green Nephrite from Three Origins

摘要:

针对产自中国新疆且末和台湾花莲以及加拿大不列颠哥伦比亚省的碧玉样品，采用常规宝石学测试、偏光显微镜观察以及电子探针和质谱分析，就其矿物组成及化学组成进行系统分析。研究结果显示，三个产地碧玉多为绿色、深绿色、墨绿色，且均含有斑点状或条带状黑色副矿物；常规宝石学特征相似，难以区分。镜下观察可见三个产地碧玉样品主要矿物成分均为透闪石，加拿大碧玉中可含少量阳起石和辉石，且末碧玉中副矿物主要为钙铬榴石，加拿大和花莲碧玉中副矿物主要为钙铝榴石。电子探针分析结果表明，样品主要矿物是透闪石，且随Fe、Cr含量的增加碧玉颜色显示出由浅至深的变化。电感耦合等离子质谱仪（LA?ICP?MS）分析结果显示，花莲碧玉Sc含量明显高于其他两个产地，可视为该产地碧玉的化学成分标型特征。

Abstract:

The mineral and chemical compositions of green nephrite samples from Qiemo County， Xinjiang Uygur Autonomous Region， Hualien County， Taiwan， China， and British Columbia， Canada were systematically analyzed by gemological tests， microscope observation， electron probe X-ray microanalyser（EPMA）， and laser ablation microprobe inductively coupled plasma mass spectrometry（LA- ICP- MS） analysis. The results show that the green nephrite from the three origins are mostly green-dark green， containing spotted or banded black accessory minerals， whose gemological features are similar and difficult to distinguish. Under the microscope， it can be seen that the main mineral composition of green nephrite samples from the three different origins are tremolite， but that from Canada can contains a small amount of actinolite and pyroxene. The Qiemo green nephrite is calcium-chromium garnet， and the Canada and Hualien green nephrites are grossularite. The results of EPMA show that the main mineral of the samples are tremolite， and the color of green nephrite changes from light to dark with the increase of Fe and Cr content. The results of LA-ICP-MS show that the content of Sc in the Hualien green nephrite is significantly higher than that in the other two origins， which could be regarded as the typomorphic characteristics of the chemical composition of the Hualian green nephrite.