云南的镁铝榴石

红色的镁铝榴石是云南最重要的宝石资源之一。由于其粒度大、裂纹少、产量较多，开发利用十多年来国内外市场情况良好。镁铝榴石形成于滇东南晚第三纪岩筒状的玄武质次火山角砾岩中，角砾岩成分复杂，其中包含有镁铝榴石和铬透辉石等可作宝石材料利用的角砾和晶屑。角砾岩通过地表风化，成为可以开采利用的宝石矿床。研究得知，Cr^3 离子是红色的主要色素离子，根据其含量的不同，可分为三种类型：含铬镁铝榴石、微铬镁铝榴石和镁铝榴石。

PYROPE FROM YUNNAN PRPOVINCE, CHINA

Red pyrope is one of the most important gem resources in Yunnan. The pyropes from YunnanProvince, which are characterized by the large grains, less cracks and high production, have been soldvery well in the world market for over a decade since they were mined. The pyropes are found in theNeogene subvolcanic basaltic breccia pipe. The rubbles and crpetals of prrope and chrome-diopsidewhich can be used as gem materials are found in the breccias whose component is very complex. Thebreccias whiCh are subjected to weathering can become gem deposit. The research shows that Cr3+ ion isresponsible for the red color of pyrope. According to the content of Cr3+ ions in the pyrope, the pyropescan be divided into three types: chromium-bearing pyrope, microchrominn-bearing prrope and pgrope.