| Burmese amber was formed in the Cretaceous period between 80 million and 100 million years ago.It is one of the oldest ambers in the world.Because of its high maturity,large output,and relatively low price,it has become a new hot spot for amber investment collection.In the market,the transparent Burmese amber based on hue,chroma,brightness and fluorescence performance are brown amber,gold amber,blood amber,and tea amber.There is no set of repeatable test methods to define the color of transparent Burmese amber.Therefore,63transparent Burmese ambers for regular gem testing,element testing,spectrum and color analysis,and compare them with other ambers were chosen and synthetic resins to provide a basis for identification and scientific research,to achieve Burmese amber color grading standards,and unify understanding between merchants and consumers.Burmese amber is rich in color and has a wide variety of inclusions.Using elemental vario cube,the C、H and O mass fractions of Burmese amber are distributed in a relatively stable range.The average C,H,and O mass scores of Burmese amber are:81.7%,12.7%,and 5.38%,while the average C,H,and O mass fractions of Burmese amber are 81.7%,12.7%,and 5.38%.The mass scores of H and O are 77.83%,9.63%,11.53%,which can distinguish the origin.The N content of synthetic resin with an average of 2.33%is higher than that of Burma and Baltic amber,and the content of C and H is lower than that of natural amber.The C and O mass fractions and C and H mass fractions of Burmese amber,Baltic amber and synthetic resin have good zoning and correlation.With the increase of C content,the H element tends to increase,and the O element content decreases.Burmese amber is more petrified than Baltic amber.Using infrared spectroscopy,1227cm-1and 1148cm-1are characteristic absorptions in the fingerprint region of Myanmar amber infrared spectrum,which can be used as a basis for judgment of origin;the infrared spectra of Burmese amber of different colors all show good uniformity.The absorption peak of lighter Burmese amber near 1717 cm-1is slightly weaker than that of darker Burmese amber.63 ambers all have the characteristics of the absorption peak of Burmese amber infrared spectrum.The infrared spectrum of Baltic amber is different from that of Burma.There is a wide and gentle absorption shoulder near 1265cm-1,which is combined with the peak at 1158cm-1to form a characteristic"Baltic shoulder".The three peaks of the infrared absorption spectrum of synthetic resin at 2961cm-1,2930cm-1,and 2863cm-1and natural amber at 2927cm-1and 2858cm-1can be used to identify imitation products.Using USB2000+fiber optic spectrometer with CIE 1976 uniform color space,combined with Yunnan local amber grading standard,and using SPSS Statistic 23 as cluster analysis of the colorimetric parameters of amber samples（L*,a*,b*values）.Burmese amber can be divided into golden amber,tea amber,blood amber,and brown amber.The cluster center of the golden amber is L*=35.56,a*=0.5587,b*=29.866;The cluster center of tea amber is;the cluster center of blood amber is L*=27.442,a*=5.132,b*=14.161;the cluster center of brown amber is L*=22.17,a*=0.3464,b*=19.189.The hue angle and main hue of Burmese amber are:46°≤h*ab<55°red orange,72°≤h*ab<90°orange yellow,90°≤h*ab<108°yellow,108°≤h*ab*<126°green and yellow.There is approximately a positive correlation between lightness L*and saturation C*.The brightness L*is concentrated between 17 and 44,divided into 4 levels.Using the data of lightness and chroma,a set of color quality grading system of Burmese amber was established,which has a grading gradient with strong repeatability and readability. |
