The Study On Gemological And Mineralogical Of Black-jadeite From Myanmar

The predecessors did a lot of research on green,Fei-color and pink-purple jadeite but The systemic gemological researches on black-jadeite is not comprehensive and thorough lacking of scientific experimental data and spectroscopical characteristics.There are also some misunderstandings of black-jadeite for people.This situation is very unfavorable for the systemic gemological researches on black-jadeite and development of its market.A comprehension summary to gemology characteristics of the black-jadeite and the study of its jewelry culture is meaningful.In this paper,The macroscopic features,gemological characteristic,mineral composition,mineral structural characteristics,spectroscopical characteristics and cause of colour of blackjadeite are studied by the means of several conventional gemmological methods: Macroscopic observation of market specimens,refractometer,hydrostatic weighing method,observation under the polarizing microscope,X-ray powder diffraction(XRD),Infrared spectroscopy(IR)and Raman spectrum.Based on the above research content,the cause of black-jadeite is reasonably speculated.Through the macroscopic observation of black-jadeite,it is found that black-jadeite can be classified reasonably: according to the shape of black macroscopic distribution in black jade,black jade can be divided into: block(pulse),cemented,disseminated;According to the the color of the black-jadeite can be divided into black jade,pure black,gray black,grayish white;according to the black-jadeite germplasm can be divided into Ice-black jadeite,“black chicken” jadeite.Polarizing microscope observation,The black-jadeite shows columnar,granular,fibrous and fragmentation crystal structure.There are some black impurities in the black-jadeite,which are small dot and irregular shape,theirs occurrence state: Distributed in the interior of jadeite crystals: one in the form of mineral inclusions and the other along the cleaved edges of jadeite crystals;Distributed along the jadeite mineral crystal gap;Distributed in the micro-cracks of jadeite minerals: the fracture surface of the jadeite crystal and the fragmentation crystal structure.The X-ray powder diffraction(XRD)showed that the main mineral component of black-jadeite is jadeite and the spectrum shows the weak graphite diffraction peak.The IR spectrum showed that the main mineral of black jadeite is jadeite;Raman spectrum shows that the black part of black-jadeite has the characteristics of jadeite and graphite carbon,and the white part of black-jadeite has jadeite Raman peak.Combined with the results of X-ray powder diffraction(XRD),it is known that the black impurities in the black-jadeite are graphite carbon.It is speculated that black-jadeite is formed in the process of metamorphism of jadeite.Due to the carbonization of organic gases,graphite carbonaceous matter is precipitated and distributed in jadeite in a dispersed state.The fine graphite carbonaceous material will absorb the light incident on the interior of the jadeite,resulting in a decrease in the transparency of the jadeite sample.The absorption of the transmitted light is different depending on the carbonaceous intensity,which makes the jadeite form different degrees of black.Produced a black-jadeite.