软玉中的一种绿色斑点——钙铝榴石

近年来我国软玉市场上见到一种比较罕见的局部带有翠绿色矿物的软玉,其矿物组成及绿色斑点还没有相关研究报道.本文应用高倍率光学显微镜观察到绿色矿物的晶形较完整并呈斑点状分布,再利用拉曼光谱仪和能量色散荧光光谱仪对样品及其绿色矿物进行无损分析.结果表明,该软玉样品主要矿物成分为透闪石,呈斑点状分布的绿色矿物为钙铝榴石,钙铝榴石的主要致色元素为Cr元素,因此含Cr绿色钙铝榴石是使玉石局部呈现绿色的原因之一,与青海翠青玉、碧玉的绿色成因有一定差异.绿色石榴石多出现于碧玉中,在其他品种的软玉中一般没有见到,本文研究的玉石中出现一定数量并有一定晶体形态的绿色钙铝榴石对研究该类玉石的产地及矿床成因具有重要意义.

The Green Spots in Nephrite-Grossularite

Recently, a variety of nephrite with emerald green spots appeared in the nephrite market. There is no report on the mineral composition and green spots for this type of nephrite. Under a higher magnification optical microscope, the complete crystal shape, microstructure and the distribution of the green spots in nephrite were observed. The chemical compositions and mineral phases have been identified using Raman scattering spectrometer and Energy-Dispersive X-ray Fluorescence Spectrometer (ED-XRF) techniques. It was found that the main mineral composition of nephrite is tremolite and the green spots are grossularite. The main coloring element in grossularite is Cr. Therefore, the Cr-bearing grossularite is the main reason for the green spots occurring in the nephrite. It differs from the colouration of traditional green nephrite (jasper) and Qinghai CuiqingYu. The green garnets usually have been observed in jasper, and never found previously in other varieties of nephrite. A certain number of green grossularites with crystal shapes in the nephrite is very important for the study on the origin of this nephrite deposit and the place of its origin.