The Study On Gemological And Mineracal Characteristics Of Blue-green Jadeite And Its Crust From Guatemala

In this paper,blue-green jadeite samples which have crust collected from Guatemala,were studied by normal Gemological testing,optical microscopy,Electron probe Microanalysis?EPMA?,X-ray powder diffraction?XRD?,infrared spectroscopy?IR?,Raman spectrum and Uv-vis-NIR spectrum on their basic gemology mineral composition,texture,mineral composition,chemical composition and spectral characteristics.Guatemala jade samples internal jade are blue-green with yellow sand crust.The result of polarzing microscope observation shows that the features from the jade and its crust are relevant.Most of samples selected from the internal jade and crust particles are jadeite,showing porphyroblastic texture,cataclastic texture,and local vein filling.Dark opaque impurities are observed at the crust of samples and localized alterations are observed.It is observed that the structure of crust and the crack is relatively loose.The result of PEMA and XRD tests show that the main mineral of samples and its crust are jadeite,the secondary minerals is omphacite.Besides,XRD test show that the samples probable have a few muscovite.The IR of jade and its crust showed the similar characteristic peak of jadeite in fingerprint area,the main peak is 1090cm^-1?926 cm^-1?588 cm^-1?528 cm^-1?466 cm^-1?432 cm^-1,but the different peak in functional group.The characteristic absorption peaks of jade and its crust are approximately the same,but the characteristic absorption peaks of high-frequency hydroxyl-OH(3626 cm^-1 and 3695 cm^-1)appear in the functional group region of the crust.It can be inferred that the crust contains aqueous clay mineral?such as kaolinite,etc.?and internal jade dose not.The UV-vis spectra of internal jades show 434 nm or 433 line,which is similar to the 437 nm line of Myanmar jade,but slightly shifted.Two of the samples showed a weak red region absorption peak?693 nm,670 nm,656 nm?caused by Cr³⁺.The Raman spectrum of samples mainly showed characteristic peaks of jadeite,and its characteristic peak also appears to shift to low frequency.In adiition,the Raman spectrum peaks of biotite and zeolite are also found in the samples.Color and texture evaluations can be obtained by comparing the chemical composition and structure of the blue-green jadeites of Guatemala and Myanmar,and the composition of the Guatemalan blue-green jade and its crust.According to the evaluation,the quality of Guatemala's blue-green jade is slightly inferior to that of Myanmar's same-color jade.