Critical Evidences for Identification of Heated Ambers

Based on the experimental study of the heat treatment of amber,the changes of the gemmological parameters and infrared spectra,and evolution,reworking and destroyed features of the inclusions in the amber samples before and after the heat treatment are tested and gathered and analysed by using the conventional gemmological methods and infrared spectrometer. The effect of the heat treatment of the amber samples are discussed on the origin,summing up some critical evidences for the identification of the heated ambers.The results indicate:(1)The increase of the refractive index,weakening and disappearing of the fluorescence are the important evidences for the heated amber;(2)Dish-shaped cracks,red lamina,evaporated cracks,tortoise-like cracks and oxidized cracks are the signatures for the heated ambers;(3)I=2 930 cm^-1/I=1 735 cm^-1≤1 in the infrared spectra is the fingerprint testing indicator for the heated amber;(4)Increase and combination of several peaks of carbonyl(C═O) oscillation at 1 735,1 700 cm^-1and C—O oscillation at 1 260~1 156 cm^-1represent the strong heat oxidization on the surfaces of the heated amber. The increase of carbonyl concentration is probably not only the reason to produce the red colour of the heated ambers,but also to curb fluorescence of the heated ambers.