ESR Behavior and ¹³C NMR Representation of Treated Amber and Resin

In recentjewelry market,the identification of ambers turns into a puzzle because itis difficult to differentiate among treated ambers,treated copal resins and treated resins. IR, ESR and ¹³C NMR testing methods are employed to the study on treated ambers(heat-treated or pressed) and treated resins. This study is focused on the analysis of the differentiation charater and ¹³C NMR and the resonance spectral peak for the carbon functional groups.The results show that the spinning concentration of the stable free radical in the natural resin is closely associated with the aromatic concentration,and at the same time is controlled by the geological period when it occurred,and the physiochemical environment which it existed in the post-petrification period. The clinkering in the late period,the polymerization and esterification and the unequal incorporation of foreign filling materials are the major causes of the changes in the spinning concentration of stable free radical and in the aromatic contents. The research results prove tentatively that the artificial polymerization,esterification or clinkering treatments may resulteasily in the faultbonds forthe unstable T-CH₂ carbon functional group, adeps-methyl carbon functional group and aliphatic adaptor-oxygen carbon functional group. The corresponding ¹³C NMR resonance peaks are the major basis for the differentiation between treated amber and treated resin.This study also shows thatthe relative contents of car-bonyl carbon functional group and adeps- methyl carbon functional group decrease with geological age increasing until they totally disappear,which may serve as the representative significance for the identification of the relative age of the natural resin.