Study On Gemmology And Mineralogy Characteristics Of Jadeite And Its Application In Non-destructive Origin Traceability

Jadeite is a rare and precious variety of jade.Jadeite is formed through complex geological processes under the geological background of plate subduction,jadeite undergoes complex geological processes and is mainly located in serpentinite melanges of high-pressure and low-temperature origin.Myanmar is a famous producer of high-quality jadeite,and as the production of jadeite in Myanmar decreases.Guatemalan and Russian jadeite products are constantly entering the jadeite market,and there are frequent issues such as mixed sales and difficult identification of authenticity in the jadeite market.Currently,research on jadeite mainly focuses on Myanmar production areas,and there is a lack of comparative research on traceability and identification of different jadeite production areas.The market urgently needs scientific,fast,and accurate traceability and identification technologies for production areas.In this paper,samples of jadeite from important places in Myanmar,Guatemala and Russia were collected to detect the characteristics of jadeite from different places in terms of gemmology,mineralogy and geochemistry,and to discuss the origin tracing and mineralization process of jadeite.This article takes jadeite from Myanmar,Guatemala,and Russia as the research object,conducts gemmology,infrared spectroscopy,Raman spectroscopy,ultraviolet-visible absorption spectroscopy,and LA-ICP-MS in situ microanalysis tests on samples to obtain nondestructive or slightly damaged origin identification characteristics of jadeite.Combining machine learning algorithms,using the content of chemical elements in jadeite as the origin traceability index,a jadeite origin traceability model is established,exploring the origin tracing characteristics and mineralization process of jadeite by combining petrography,mineral characteristics,fluid inclusion characteristics,etc.The main research results of this article:（1）In basic gemological testing,under microscopic magnification,Russian jadeite contains green fibrous and black impurity minerals,while Guatemalan jadeite contains many flocculent substances.The average relative density of Russian jadeite samples is slightly lower than that of other regions,while the average relative density of Myanmar jadeite samples is slightly higher than that of other regions.（2）The infrared spectrum and Raman spectrum characteristics of jadeite from Myanmar,Guatemala,and Russia show that Myanmar jadeite only displays jadeite spectral peaks,while some Russian and Guatemalan jadeites have slightly shifted spectral peaks,resulting in more complex mineral composition.Only the UV-visible absorption spectrum shows that when the sample thickness is consistent,the peak range of absorption coefficient at 430nm is greater than 1.1,and the peak absorption coefficient at 437nm is greater than 1.1,it is Guatemalan jadeite.The peak range of absorption coefficient at 430nm is less than 0.62,and the peak absorption coefficient at437nm is less than 0.66,it is Myanmar jadeite.When the peak absorption coefficient at430 nm ranges from 0.62 to 1.1,and the peak absorption coefficient at 437nm ranges from 0.66-1.1,forming a common region for jadeite from three origins.The peak absorption coefficient of different origins is positively correlated with the content of Fe and Mn elements,With certain genetic significance。（3）According to the LA-ICP-MS testing of chemical element values,Only Guatemala has slightly higher values for trace and rare earth elements,with slightly different elements Zr,Sr,Hf,and Ba.Three machine learning methods,linear discriminant analysis,random forest,and support vector machine,were used to adjust parameters and optimize the jadeite origin traceability model.The accuracy of both the origin identification training set and the test set was above 90%.The training sets and test sets of random forests and support vector machines（linear）have the best results.Screening out important indicator elements that affect the results of the origin traceability discrimination model,such as Li,Ti,Mn,Fe O,Sr,Zr,and Ba.（4）Petrographic studies show that Myanmar jadeite is mainly characterized by dynamic metamorphism and late metasomatism,Guatemala jadeite is mainly characterized by dynamic metamorphism,and Russia jadeite is mainly characterized by metasomatism.According to the study of major mineral elements,the chemical composition of Myanmar jadeite minerals is consistent with the theoretical value of jadeite.Compared with Myanmar jadeite,Guatemalan jadeite has a higher Si O₂ content,lower Al₂O₃,and Na₂O content.Russian jadeite jadeite has the highest Si O₂ content,and the lowest Na₂O content.The Al₂O₃ content is basically consistent with that of Guatemala jadeite.Among them,the isomorphic elements Fe,Mn,Ti,Mg,and Ca in Guatemalan jadeite are the most abundant.In Guatemalan jadeite samples,Omphacite jadeite solid solution mineral are commonly found.Russian omphacite minerals are found in the omphacite aegirine pyroxene region.Minerals such as galena,sphene,and barite have been found in Russian jadeite samples.Russian jadeite has an alkaline reduction environment,and it is speculated that Russian jadeite has a deeper depth and a sediment material source.（5）Through observation and test analysis of the morphological characteristics of fluid inclusions in jadeite,it is found that the majority of primary fluid inclusions and the lack of protolith characteristics in Myanmar and Guatemala are more oriented towards fluid deposition genesis（P-type）,with an average homogenization temperature of 312℃,a corresponding salinity of 7.86-9.98%Na Cleqv,and a calculated pressure value of 0.27-0.32GPa.The average temperature in Guatemala is 210℃.The salinity is 3.39～6.30%Na Cleqv,and the calculated pressure value is 0.40～0.42GPa.The temperature and pressure values in Myanmar and Guatemala are similar.The temperature and pressure are basically consistent with the formation temperature and pressure of amphibole schist.Russia has fewer primary fluid inclusions and irregular morphology,which are more indicative of metasomatic origin（R-type）.The uniform temperature of jadeite in Russian jadeite exceeds the temperature limit of the thermometer.Based on the Raman spectrum thermometer of graphite in the inclusions,the crystallization temperature of graphite from the fluid is estimated to be 595～598℃.It indicates that the formation temperature of jadeite minerals in Russian jadeite is within the temperature range of medium temperature and high pressure eclogite.According to the residual characteristics of the protolith from Russian origin,it is speculated that Russian jadeite may be of metasomatic origin（R-type）.