Gemological Study Of Nephrite Gravel

Hetian jade is one of the most fabulous treasure in China which has an irreplaceable position in every Chinese heart. It can be three different forms, according to different occurrence, as primary nephrite, gravel and slope jade. Xinjiang gravel is mainly yielded in the secondary deposit of river Yurunkax and Karakax. This paper through visual observation, microscopic observation, then by using the modern testing methods as slice observation, electron probe, the scanning electron microscope, infrared spectroscopy and Raman spectroscopy, I studied the mineral composition, structural features, surface morphology and spectrum characteristics etc. on gravel and imitating gravel, summarized its features to provide more evidence to extinguish Xinjiang Hetian jade from other nephrite.Visual observation and microscopic observation shown that gravel materials have delicate texture, oily feeling, mostly oblate spheroid, high psephicity, the fiber intertexture crystalloblastic texture mainly. There are a lot of surface dent, the point of impact and scratch grooves. It’s skin color may have a variety of colors with natural transition. Imitating gravel have rough texture, no grease luster, granuloblastic structure mainly. It can be many shapes with high psephicity. There are a few dent and scratch grooves on the surface. The skin color is gorgeous and with unnatural transition.Scanning electron microscopy shown that there were differences in the morphology of the surface between gravel and imitating gravel. The surface of the gravel is smooth and delicate, and it is almost impossible to distinguish its particles. "Pores" and pits can be seen in gravel. Visible mineral particles have been rounded partly under flow action at the bottom of pits. Imitating gravel surface is rough with bigger particles. Their surface base on the same plane, some mineral particles have been destroyed. "Pores" cannot be seen. Visible mineral particles are angular at the bottom of pits. Energy spectrum analyzer can measure C, Cl and other elements on the surface of the imitating gravel, presumably containing organic dyes.Electron probe analysis shown that The essential minera1 of Hetian jade is tremolite and secondary minerals for diopside, sphene. Iron exists mainly in the form of Fe2+ which is the main reason of it’s natural surface color.Infrared spectroscopic analysis shown that Hetian jade gravel and imitating gravel share almost the same vibrational spectra. The absorption peak position is also consistent. Their mineral compositions are tremolite. Raman spectroscopic analysis shown that Raman spectra of different kinds of nephrite and Hetian jade are basically the same. With the impurities in Hetian jade, the peak shifted. Peak intensities, shapes and sharp degrees have slightly differences.