Comparison Of The Characteristics Of Emeralds Between Pakistan And Afghanistan

Afghanistan and Pakistan emeralds have similar in appearance both from the Himalaya orogenic belt,including recently discovered trapiche-type crystals in Pakistan.In this study,emerald samples from Panjshir and Swat Valley were examined by standard gemological testing,Diamond View^TM,UV-Vis-NIR,FTIR,Raman analysis,EDXRF,and LA-ICP-MS.Our findings provide insights that can be used for separating emeralds in these two deposits while shedding light on the characteristics of trapiche-type emerald from Pakistan.The study found three-phase hexagonal inclusions consisting of water,gaseous carbon dioxide and nitrogen,and a magnesite crystal rare in Pakistan emerald,while a small carbonate mineral,2 or 3 bigger carbonate minerals and a cubic crystals of the three-phase inclusion are normal in Afghanistan emeralds.The gaseous mixture in two-phase inclusions is characteristic in both trapiche-type(CO₂+N₂)and non-trapiche samples(CO₂+N₂+CH₄)from Pakistan emeralds,but bubble is CO₂ in Afghanistan emeralds.Mineral inclusions of hematite,magnetite,rutile,graphite,and siderite are reported for the first time in Pakistan emeralds.Regular non-trapiche-type Pakistan emeralds contain high Li,Na,Rb,Cs,Cr,Mg,Fe and Sc.However,Afghanistan emeralds have high Rb,Sc,V and low Cs and Li.Logarithm plots of trace elements including Li vs Sc,Cs vs Rb and Li vs Cs,appear to be diagnostic.Through EDXRF testing,the content of Cr,Fe and Sc and Cr/V ratio in the emeralds of Pakistan is significantly higher than that in Afghanistan,while the content of V in Afghanistan emeralds is higher than that in regular non-trapiche-type Pakistan emeralds.The main chromophores in Afghanistan and Pakistan emeralds are Cr³⁺,V³⁺,Fe³⁺and Fe²⁺,of which Cr³⁺is the most important cause for green color.The strength of UV-Vis-NIR spectrum of Fe²⁺is similar with Cr³⁺in regular non-trapiche-type Pakistan emeralds,but the spectrum of the trapiche-type emerald illustrates the strong Fe³⁺band at 370 nm and the spectrum of the Afghanistan emerald shows the strong Fe³⁺band and the strength of Fe²⁺is obviously weaker than that of Cr³⁺.Infrared spectra(?c)of Afghanistan and Pakistan emeralds show that the absorption of type II H₂O is stronger than that of type I H₂O.Infrared spectra(?c)of Afghanistan emeralds show that he absorption of type?H₂O at 7142 cm^-1.The Raman spectrum of Afghanistan emeralds illustrates the peak of type II H₂O at 3598 cm^-1 is stronger than that of type I H₂O at 3606cm^-1,while only the peak of II H₂O at 3598 cm^-1 in Pakistan emeralds,which both are high-alike emeralds.Based on Raman spectroscopy,the Pakistan trapiche-type emeralds'colorless core,light green hexagonal growth zone area,and green rim are emerald,while the six black arms are a mixture of hematite and graphite.