The Gemological And Mineralogical Characteristics Of Jilin “Panlong Dark Jade”

In 2015,a large-scale jade mine was discovered in the city of Panshi,Jilin Province.This paper systematically studies the gemology and the mineralogy of the“Ponglong dark jade”with modern testing methods.The“Ponglong dark jade”is named carbonaceous slate in petrology.Through observation of rough stone,Jilin“Ponglong dark jade”is opaque,mainly black,most of the color distribution is more uniform,a small amount of sample is gray black,black and yellow,a very small amount of“Ponglong dark jade”is black and yellow.Thejade is mainly formed as plate-like,blocky,and it is oily luster to weak glass luster,uneven fracture.The range of the refractive index of this jade is 1.52 to1.54,The density of the black jade is ranged 2.72 g/cm³ to 2.80 g/cm³.The Moh's hardness is 3.89-6.23.The main structure of this kind of jade is a cryptocrystalline-fine grained and superbilled,occasionally congruent and patchy structures can be observed.“Ponglong dark jade”is composed of quartz and sericite,sometimes which contains chlorite,albite,serpentine,kaolinite,calcite,and pyrrhotite.The chlorites are classified into daphnite,pycnochlorite and iron magnesium chlorite.Calculate the chemical formula of each mineral by electron probe data.The formation temperature of chlorite is 245?.The main chemical composition of“Ponglong dark jade”are Si O₂and Al₂O₃ with a small amount of Fe O,K₂O,Mg O,Fe₂O₃,Na₂O,Ca O,Mn O,Ti O₂,and Cr₂O₃.The total amount of rare earth elements is stable,which is about 200ug/g,light rare earth elements are enriched,and the LREE/HREE values are very large at6.83-10.04.The La N/Yb N values range from 6.19 to 9.49,showing negative Eu anomalies with?Eu values between 0.59 and 0.73.Testing the sample by FTIR,the characteristic spectrum was acquired.There are two classical infrared spectrum,one is the combination of the infrared spectrum of quartz and sericite,and the other is the combination of quartz,sericite and chlorite.Testing the five samples with laser raman,the results in line with other analysis.We gained the spectra showing that the jade is combined with quartz,sericite,feldspar and graphite.However,unlike the spectra of gray samples that show extreme weak peak of graphite,the spectrum of black one show much strong and clear peak of graphite.But the gray one contains more chlorites than the black one.Therefore,we can infer that graphite and chlorite resulting the color.