Font Size: a A A

The Study On Gemological And Mineralogical Characteristicsof Nephrite In Dahua, Guangxi

Posted on:2016-01-24Degree:MasterType:Thesis
Country:ChinaCandidate:J M DuFull Text:PDF
GTID:2180330461494969Subject:Gemology
Abstract/Summary:PDF Full Text Request
Gemological and mineralogical properties and characteristics of tremolite jade from Dahua Guangxi province were studied and compared with nephrites from other localities in this paper. The difference may provide instructive insights for jade identification and mining exploration. The origin of Dahua tremolite jade deposit was deduced based on observation and analysis results.Dahua tremolite jades are mainly bluish white and grayish green, of which the surfaces are weathered. Among samples studied, the majority are slightly transparent to nearly opaque, with weak luster being waxy to greasy. White and black dots or veins impurities were observed. For the Dahua tremolite jade samples studied through the conventional gemological test, the density of range from 2.90 to 2.97 g/cm3, being 2.94 g/cm3; Mohs hardness is range from 5.32 to 6.06, being 5.70; Refractive index vary from 1.60 to 1.62, lower than the standard value of nephrite.Polarized microscopic observation reveals the texture of Dahua tremolite jade mainly as panniform fiber crystalloblastic and microscopic fiber crystalloblastic. The wall rocks are diabase and tremolite-dolomite, with their texture being diabasic and granular accordingly. The main minerals found in tremolite jades samples and wall rock samples are fibroid and fascicular tremolite, while the accessory minerals being granular diopside, calcite, chlorite, quartz and fibroid actinolite. The tremolite jade surface exhibits microscopic fibrous interlocking texture, orientated microscopic fibrous texture and microscopic laminar texture under on SEM observation.The composition of samples were investigated by Infrared spectroscopy, X-ray powder diffraction and EPMA. All the results are very close to those of standard tremolite. The main chemical composition contains Ca O, Mg O, Si O2, minor contains Fe O, Mn O, Na2 O, K2 O, Al2O3, Ti O2, etc. Thus, the main minerals are identified as tremolite. Compared with the back scattering BSE images, the mineral compositions of samples studied are in good agreement with observation on thin sections under polarized microscope, with the primary mineral being tremolite, diopside and chlorite, as well as apatite, sphene and andradite.Based on data obtained in this study, it can be deduced that the Dahua tremolite jade deposit belongs to magmatic hydrothermal metasomatic deposit, which can be originated from contact metasomatism and hydrothermal metasomatism between hydrothermal solution brought by basic intrusive rock or magma, such as diabase, and tremolite limestone under certain temperature and pressure.The gemological and mineralogical properties of Dahua tremolite jades are basically consistent with tremolite jades from other localities. Considering that Hetian jade no longer stands for nephrite form Hetian, Dahua tremolite jades can be called as Hetian jade according to the national nomenclature standard. Further study on Dahua tremolite jades are needed for future mining exploration.
Keywords/Search Tags:Guangxi Dahua, tremolite jade, gemological property, texture, composition
PDF Full Text Request
Related items