不同颜色青海软玉微观形貌和矿物组成特征

青海软玉颜色丰富,近年来对青海软玉矿物学的研究不少,但针对不同颜色青海软玉矿物学特征的研究还存在欠缺。本文利用偏光显微镜、扫描电子显微镜、电子探针及粉晶X射线衍射仪器,从透闪石微形貌特征、微观结构、矿物组成及结晶度四个方面,研究了青海软玉颜色与矿物学特征的对应关系。结果表明:白玉、烟青玉、糖玉中透闪石主要为纤维状,显微纤维变晶结构,结晶度为96. 12%～96. 88%;青白玉和翠青玉中透闪石主要为叶片状,显微叶片变晶结构,结晶度为97. 35%,97. 32%;青玉和碧玉中透闪石主要为叶片状,显微叶片-隐晶质变晶结构,结晶度为95. 48%,95. 29%;黄玉中透闪石主要为柱状,显微柱状变晶结构,结晶度为97. 84%。青海软玉主要组成矿物均为透闪石,含量在95%以上,部分次要矿物如翠青玉中的榍石、黄玉中的钙长石、青玉中的菱镁矿、碧玉中的铬铁矿、糖玉中的斜黝帘石只出现在特定颜色的青海软玉样品中。研究认为不同颜色青海软玉矿物学特征确实存在差异,这些特征为研究不同颜色青海软玉成矿环境及成矿条件提供了科学依据。

Micro-morphology and Mineral Composition of Different Color Qinghai Nephrites

BACKGROUND: Qinghai nephrites show different colors. In recent years, there have been a lot of studies on Qinghai nephrite mineralogy, but the studies on the mineral characteristics of Qinghai nephrite with different colors are lacking.
OBJECTIVES: To study the relationship between color and mineralogical features of Qinghai nephrites.
METHODS: Polarizing Microscopy, Scanning Electron Microscopy, Electron Probe Microanalyzer and Powder X-ray Diffraction were used to analyze the microtopography, microstructure, mineral composition and crystallinity of tremolite.
RESULTS: Tremolite in white, blue-violet and brown Qinghai nephrite are mainly fibrous and have micro-fiber blastic texture with crystallinity of 96.12%-96.88%. Tremolite in green-white and viridis Qinghai nephrite are mainly foliated, and has micro-foliated blastic texture with crystallinity of 97.35% and 97.32%, respectively. Tremolite in green and azure-green Qinghai nephrite are mainly foliated, and have microscopic blade-cryptocrystalline blastic texture with crystallinity of 95.48% and 95.29%, respectively. Tremolite in yellow Qinghai nephrite is mainly columnar, and has micro-columnar blastic texture and crystallinity of 97.84%. The main mineral different color Qinghai nephrite is tremolite, with content of more than 95%. Some minor minerals only appear in the specific color Qinghai nephrite, such as titanite in viridis Qinghai nephrite, anorthite in yellow Qinghai nephrite, magnesite in green Qinghai nephrite, chromite in azure-green Qinghai nephrite, and clinozoisite in brown Qinghai nephrite.
CONCLUSIONS: There are differences in mineral features of Qinghai nephrite in different colors, which provide a scientific basis for the study of ore-forming environments and conditions of Qinghai nephrites in different colors.