NONG Pei-zhen1, ZHOU Zheng-yu1,2,3*, LAI Meng1, ZHONG Qian1, WANG Han1, GUO Kai-peng1, LI Ying-bo1, QIAO Xin1, ZHANG Ling-min1
( 1. Ocean and Earth Science School, Tongji University, Shanghai 200092, China;
2. Shanghai Gemstones and Materials Engineering & Technology Research Center, Shanghai 200092, China;
3. Laboratory of Gem and Technological Materials, Tongji University, Shanghai 200092, China )
Abstract: There are veins of nephrite in the Maxianshan area, Lintao County, Gansu Province. In this paper, the green, yellowish green and brown colored nephrite samples were investigated using the conventional gemological method, infrared spectroscopy, electron probe, scanning electron microscope, and polarizing light microscopy. The results show that the nephrite samples have the spotty measured refractive indexes of 1.61, densities of 2.917－2.941 g/cm3 ( not including the weathered layer), Mohs hardnesses of 6－6.5, with greasy luster and high toughness. The nephrite samples contain essential mineral of tremolite (w(SiO2)=57.06%－58.44%, w(MgO)=23.42%－24.13%, w(CaO)=12.24%－13.04% ), and auxiliary minerals of diopside, epidote, apatite, sphene, and clinozoisite, with major micro-fiber crystalloblastic or felt-like crystalloblastic textures. All these characteristics are consistent with those of the China national standard of nephrite. It is believed that the green color intensities of samples could be related to the Fe contents. In addition, there are white weathered layers with brown dendritic substances (with nickname of "ant feet" or "algae stripes" ) distributed along fissures in nephrite, and brown transition layers between the white weathered layer and nephrite body.
Keywords: nephrite; mineral composition; chemical composition; texture; dendritic substance; the Maxiashan area
ACTA MINERALOGICA SINICA Vol. 39, No.3, 2019, page 327-333
