块状水钙铝榴石玉的点状绿研究及其鉴别

极椐显微镜下、红外光谱和Ｘ射线衍射的研究，表明块状水钙铝榴石玉的主要矿物成分是水钙铝榴石，并有含量不等的透辉石和方解石等。它的折射率为１．７２０左右，相对密度为３．４０～３．５０。在水钙铝榴石矿物中分布有密集程度不等的点状绿，这些点状绿多呈圆形或泪滴状，其第径约为０．１～１．０ｍｍ。每个点头绿的中心都有大小为０．０１～０．５０ｍｍ的黑斑。多数黑斑中心由一个黑点组成，但也有由璜工两个以上的黑点构成。

STUDY AND IDENTIFICATION OF POINT-LIKE GREEN IN MASSIVE HYDROGROSSULAR JADE

The study on massive hydrogrossular by means of polar microscope, infrared spectra and Xray shows that it consists mainly of hydrogrossular, with a little amount of diopside and calcite. Its refraction index is about 1. 720 and its relative density 3.40-3. 50. Point-like green about 0.1-1.0 mm in grain size is distributed in hydrogrossular and shows the shape of circle or tear. The center of pointlike green consists of black point whose grain diameter is 0.01-0. 50 mm. The center of almost all point-like green consists of only one black point. The boundary between the black point and its surrounding green circle is clear. The point-like green has also a clear boundary with the hydrogrossular encircling it. Black point in green circle center is translucent under thin section by magnification 250X, transparent by magnification 400X. The result of energy spectrum analysis shows that black point consists of silicate mineral containing higher amount of iron than chlorite outside the circle. The black point results from aggregation of iron produced by chloritization of hydrogrossular. The point-like green is an important character of hydrogrossular.