Study On Mineral Composition And Genesis Of Green Nephrite In Ospinsk,Russia

The green nephrite produced at the Ospinsk is the best quality green nephrite in the world.In this paper,through a variety of modern testing techniques,the gem mineralogical characteristics of the green nephrite in the Ospinsk are studied.The green nephrite in the Ospinsk’s color is mainly green and dark green,with uniform color distribution and black dot-like inclusions.The polished surface of the sample is from oily luster to weak glass luster and translucent.The relative density range is 2.98-3.00g/cm³,the refractive index range is 1.60-1.62,and the Mohs hard-ness is 5.75-5.82.The main structure of green nephrite in the Ospinsk is cryptocrysta-llinemicroscopic and unequal-grained crystal structure.The main mineral component of green nephrite in the Ospinsk is tremolite,which may contain a small amount of chromite,chloriteand so on.The main chemical components are SiO₂,MgO,CaO,and may contain a small amount of FeO,Al₂O₃,NiO,Cr₂O₃,MnO.The data obtained and calculated under the detection of electronic probes,although most of the Mg/（Mg+Fe）ratio is between 0.90-1.00,but generally concentrated between 0.90-0.92,the ratio is lower.The measured data of actinolite is around 0.89,it can be speculated that some tremolite in the sample is in the transition stage to actinolite.The ratio of Fe/（Fe+Mg）in the sample ranges from 0.08 to 0.11.The Fe/（Fe+Mg）ratio of serpentine Hetian jade is greater than 0.06.The content of Cr,Co and Ni in the samples of the LA-ICP-MS test data of the green nephrite of the Ospinsk conforms to the content range of the origin of serpentine nephrite,which corroborates the genetic types of the jasper of the Ospinsk.The total amount of rare earth elements does not change much,the content is low,and the average content is 1.498ug/g.There is a slight negative Eu anomaly,=0.053-0.422,Nb shows a slight loss,the value of Nb/Ta is 1.04-5.00,La_N/Yb_N=5.39-15.53,LaN/SmN<1,Sr/Ba ratio is 1.06-2.11,the serpentinized peridot that formed green nephrite has a lowerΣREE content,LREE is weakly enriched relative to HREE,and exhibits Eu weak negative anomalies.It was found that the data detected in the infrared spectrum and Raman spectrum detected by the transmission method were consistent with the standard spectrum of amphibole minerals.The relative shift of the peak and peak position proves that the main component of the Ospinsk,the main component of the green nephrite in the Ospinsk,is in the transition to the sunburst.The green nephrite at the Ospinsk was originally produced in the ophiolite in the Eastern Sayan Mountains,and the green curtain-hornblende transition facies in the metamorphic rocks at the bottom of the ophiolite.Under the condition of low temperature hydrothermal fluid,the ultrabasic rock of forsterite and the low temperature hydrothermal fluid interact to form serpentine.Serpentine is then contacted with surrounding rocks rich in silicon and calcium to form tremolite,which is the main component of green nephrite in the Ospinsk.