Gemmological Characteristics of Illite Jade

The gemmological characteristics of illite jade (the popular name with "Zipao jade") in the market of China are analysed by using the conventional gemmological methods and mordern testing methods such as laser Raman spectrometer,XRD and IR.The results indicate that the jade mainly consists of illite and a small quantity of feldspar,quartz,hematite,siderite and rutile,which is argillaceous sedimentary rock.The colour of illite jade is of distinct gradation which is related to the content of hematite in different sedimentary bed.