The Study On Gemmological And Mineralogical Characteristics Of Amazonite From Three Different Origins

Amazonite is a common medium and low grade gemstone,belonging to the variant of microcline,which has become popular in the jewelry market in recent years due to its unique green,blue or blue-green color.This article uses conventional gemological testing methods and modern large-scale instruments?Scanning electron microscopy,X-ray powder diffraction,electron probe,infrared spectroscopy,Raman spectroscopy,laser ablation inductively coupled plasma mass spectrometry?LA-LCP-MS?,etc.?to test and analyze the conventional gemological and mineralogical characteristics of amazonite samples of three different origin.Observing the mineral structure of amazonite under Polarized Microscope;Determination of mineral composition of amazonite by XRD;Determination of main and trace elements in amazonite by LA-LCP-MS;Study on the Spectral Features of amazonite by IR and Raman.A lateral comparison of gemological and mineralogical characteristics between amazonite samples of three different origins is carried out,and the results provide basis for the identification of the origin of the amazonite samples.General gemological characteristics have little difference among amazonite from three different origins.The refractive index is 1.510¹.530,the birefringence is1.510¹.530,the relative density is 2.46².55,Mohs hardness is 6.27⁶.75.The mineral composition and chemical composition of amazonite samples are basically the same,the microstructure of amazonite sample from Xinjiang and Mozambique is more compact.The unit cell parameters of the Xinjiang origin sample are the largest,and the Madagascar origin samples are the smallest.The infrared and Raman peaks of amazonite are greatly affected by the Si/Al ordering degree,and there are great differences in the amazonite samples from different producing areas.Infrared absorption and Raman scattering peak are 1140 cm^-1?1085 cm^-1?1052cm^-1?1018 cm^-1?772 cm^-1?728 cm^-1?650 cm^-1?607 cm^-1?584 cm^-1?537 cm^-1?467 cm^-1?430 cm^-1 and 1126cm^-1?998cm^-1?813cm^-1?750cm^-1?650cm^-1?510cm^-1?480cm^-1?290cm^-1?150cm^-1.Infrared and Raman spectra can separate Xinjiang and Madagascar amazonite samples.The absorption peaks of UV-Vis absorption spectra of amazonite samples are 210nm,250 nm,280 nm,320 nm,380nm,640 nm,and 730 nm,which are related to trace elements in amazonite.The amazonite samples contain many trace elements,and there is a correlation between the color and trace element content.It is inferred that the color of the amazonite is caused by trace elements Pb mixed into the crystal lattice.The content of trace elements and UV-visible absorption spectra in amazonite samples of different origin are different and the difference can be used as the basis to identify their origins.