高铬刚玉：湖南沅水金刚石包裹体中发现的一种高压矿物

对湖南沅水金刚石中的包裹体矿物含铬刚玉进行了矿物学研究。确认合铬刚玉中铬的最高质量分数可达19．31％。根据EPMA分析，高铬刚玉的晶体化学分子式为（All683，Cro298，Fe0.010，Mn0．008，T10．0。4，Sb．001）2．0040s，获得了该样品的X射线粉末衍射图谱，并在此基础上进行了Rietve...

A species of high pressure mineral:The high-chromium corundum(ruby) as an inclusion in diamond from the Yuanshui,Hunan,China

The mineralogy of a diamond inclusion that is the corundum containing high chromium from Yuanshui,Hunan,China has been investigated.It is confirmed that the highest content of chromium in the chromium-contained corundum may reach 19.31%.According to the EPMA analysis,the formula of the high-chromium corundum is(Al1.683,Cr0.298,Fe0.010,Mn0.008,Ti0.004,Si0.001)2.004O3.Based on the X-ray powder diffraction pattern and the method of full spectrum Rietveld fitted refinement,the crystallographic parameters were obtained as the following: R-3c,a=0.4765 nm,c=1.3007 nm,Z=6,and the trivalent chromium and aluminum ions occupy the same crystal-chemical position.Although the crystallographic parameters of the corundum suggest that it has regressed to the ordinary pressure state,the high chrome content implied that it had undergone a high-pressure environment.Thus,it can be regarded as a kind of index mineral indicating a high-pressure environment.The discovery of high Cr content of the Yuanshui corundum as a diamond inclusion suggested that the diamonds in this area were possibly from eclogite xenoliths.