Study on Mineral Components and Geological Background of Nephrites from Three Localities in China

In order to determine the mineral components of the nephrites from Manasi (Xinjiang), Geermu (Qinghai Province) and Liyang (Jiangsu Province), and to understand the relation between the mineral components and properties of the nephrites and to provide the basical data for the determination and valuation, the genesis, structures, mineral components and chemical compositions of the nephrite samples from the three localities are investigated by using the polarizing microscope, electron microprobe and X-ray powder diffraction.The results show that the nephrite samples from the three localities are consisted of tremolite with the varied amounts of Mg and Fe in the crystals.The chemical compositions of the tremolite in the nephrite sample from Manasi are very similar to that of the actinolite.The geological background of the samples from Manasi differs from that of the samples from Liyang and Geermu, the former is formed in ultramafite and contains more FeO_T and MgO, while the latter is formed in the contact zone between neutral to acidic igneous rocks and dolomitic marble, with lower content of FeO_T.The colour, tenacity and transparency of the nephrite samples are largely dependant on the conditions of geological background.