The Petrological Characteristics Features And Quality Evaluation Of Hetian White Jade

As a precious heritage and art treasure in the treasure-house of the Chinese culture,Hetian jade is popular both at home and abroad.Among them,Hetian white jade is more popular.This paper takes white jade as the research object and combines with the comparison with Qinghai white jade and Russian white jade to carry out the study on quality evaluation of the petrology and gemology of it.The paper also summarizes the difference in petrographic features and gemological features of white jade from different producing areas including Xinjiang Hetian white jade to seek the features for the identification of the producing area of Hetian white jade.Combining with market research and analysis,it analyses the quality evaluation and puts forwards suggestions for the development of Hetian jade culture industry.Main conclusions are as follows:?1?The study on petrography.The white jade from Xinjiang,Qinghai and Russia are mainly tremolite.For Xinjiang white jade,most of them are of the felt-like texture and the micro fibrous cryptocrystalline texture.A few Qinghai white jade and Russian white jade with good quality are also of the micro fibrous cryptocrystalline texture.Most of them are of micro granular crystalloblastic texture and micro leaf-like crystalloblastic texture.There is a little apatite,calcite,normal hornblende,diopside and so on in all producing areas.?2?The study on rock and mineral element geochemistry.The electron probe?EPMA?shows that the major chemical constituents of the minerals in white jade from these three producing areas are stable with few differences.And they all belong to tremolite in calciferous amphibole.The Russian white jade is differentiated from Xinjiang white jade and Qinghai white jade with lower Al³⁺/Ca²⁺+Na⁺+K⁺.The ratio of Al³⁺/Ca²⁺+Na⁺+K⁺in Qinghai white jade is over 0.99 and is stable,which is a feature that the other two areas do not have.For Qinghai white jade,the ratio of Ca²⁺/Ca²⁺+Na⁺+K⁺is concentrated and higher,which is a clear distinction of it compared with Russian white jade and Xinjiang white jade.The paper also draws a recommended chart for these three producing areas of white jade with ratio of Mg²⁺/(Mg²⁺+Fe²⁺),Al³⁺/Ca²⁺+Na⁺+K⁺,and Ca²⁺/Ca²⁺+Na⁺+K⁺,which provides important evidence for the distinction of these three producing areas.The major elements analysis by XRF shows that the SiO₂,MgO and CaO in samples from different areas are quite stable.It is similar with the data detected by the electron probe.It also indicates that the major mineral composition is tremolite.The content of CaO in Qinghai and Xinjiang white jade is 13.8%and 13.45%,which is higher than that of Russia.In the minor constituent of samples,the content of Al₂O₃ in Russian white jade is 0.86%,and the content of K₂O is 0.19%,which is higher than that of the other two areas.The content of Na₂O in Qinghai white jade is0.30%,which is higher than that of the other two areas.?3?The study on features of spectrum.The result of XRD shows that the diffraction peak of the white jade from these areas are almost the same and there is only a slight difference in individual peak,d value and the strength in samples from different areas.Generally,the higher peak is about 3.13?,8.54?,3.28?,and 2.71?.Among them,the peak in 3.13?is the highest.This is consistent with the diffraction peak of tremolite in the International Centre for Diffraction Data.Besides,the cell parameters are close to the theoretical value of tremolite.The major difference is that the diffraction peak strength of Xinjiang white jade is weaker than that of the other two samples and its peak is not sharp but diffuse.The mineral particle in the sample is relatively small and the jade is exquisite with lower transparency and remarkable oily luster.The analysis by infrared spectroscopy?IR?shows that the absorption of the infrared spectroscopy in white jade of three areas mainly occurs in the high frequency zone from the range of3700-3600cm^-1 and 1200-800cm^-11 as well as low frequency zone from the range of800-600cm^-1 and 600-400cm^-1.The charts of all areas are almost the same and they are consistent with the standard infrared spectroscopy of the tremolite.It shows that white jade from three areas is made up by purer tremolite with few contents of impure minerals.It is shown by Raman spectroscopy?Raman?that the highest peaks of all areas occur at 1060,675 and 223,which are the characteristic spectra peaks of amphibole.Within the range of 3500-3800 cm^-1,there is only one spectral peak of3675cm^-1 in samples of white jade.However,in the samples of light greenish white jade,there are two spectral bands at the same site with 3675 and 3662cm^-1.It speculates that the shade of the color affects the vibration of the spectral peak from the range of 3500 to 3800cm^-1.?4?Comparative study and quality evaluation of similar products.Similar products of Hetian white jade have been tested by regular gemological instrument,XRF,XRD,infrared spectroscopy,and Raman spectroscopy.All tests showed that the major mineral composition of quartzite jade is quartz,the major mineral composition of Carbonate jade is dolomite,and the major mineral composition of hsiuyen jade is serpentine.Thus,they are differentiated from Hetian white jade.Finally,combining with the analysis of market research on the quality evaluation standard of Hetian jade and summarizing the process characteristics of Hetian jade in different dynasties,it analyzes the market situation of Hetian jade and puts forwards reasonable suggestions for Hetian Jade culture industry.