南阳独山玉的矿物学研究

南阳独山玉呈脉状产于河南省南阳市独山透闪石化辉长岩岩体内。笔者选择了各种代 表性样品(白玉、绿玉、白绿玉,棕黑色玉),对其进行了光薄片显微镜观察、探针、电镜、X光、红外等分析以及显微硬度测定。研究表明,独山玉在矿物成分上极为独特,以高钙、高铝、贫硅为特征,如:“纯”钙长石、黝帘石、珍珠云母等。除此之外,尚有一系列含铬矿物,如:铬绿帘石、含铬白云母—珍珠云母,含铬黑云母—金云母、铬蒙脱石、铬铁矿。这表明独山玉是在较特殊的地质环境下形成的,起交代作用的热液成分以钙为主,而铬对独山玉呈绿色、翠绿色有很大关系。

Mineralogical Studies of Jades from Dushan, Nanyang

The Dushan jades of Nanyang occur as veins in the tremolitized gabbro body. Various sorts of typical samples (white jade, green jade, white-green jade, brownish black jade) have been selected to perform polished and thin section microscopic observation, EMP, XRD and infrared spectral analysis, microhardness determination and SEM observation.The results of these studies show that Dushan jades are very peculiar in mineral composition, with "pure" anorthite and zoisite as the main minerals associated with a series of Cr bearing minerals, such as chrome-epidote, chromian muscovite margarite, chromian biotite-phlogopite, volchonskoite and chromite. Rock-forming minerals are characterized by high calcium, high aluminium and poor silicon, suggesting that Dushan jades were formed in a rather unusual geologic environment. Due to integrated control of original rocks and late-stage hydrothermal fluids, the main products are Ca-bearing aluminosilicates. With the intensification of hydrothermal metasomatism, the minerals might haev evolved in order of anorthite-zoisite, epidote-muscovite, and margarite-volchonskoite. Many minerals of Dushan jades contain chromium, which must have had much to do with the green and bright green colors of Dushan jades.