Influences on Baltic Amber Spectral Characteristics Under Thermal Optimization With Multiple Conditions
DAI Li-li1, SHI Guang-hai2*, YUAN Ye2, JIANG Xue1，LIU Wen-qing2
1. Jewelry Testing Laboratory, Guobiao (Beijing) Testing & Certification Co., Ltd., Beijing 100088, China
2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geoscience, Beijing 100083, China
Abstract：Possibly Derived from ancient Pinaceae pinus or Cedrusplants, ancient Araucariaceae Agathis plants or ancient Sciadopityaceae Sciadopitys plants, Baltic ambers are the natural fossilized resins undergone a variety of geological reworkings. Incorporating succinic acid Baltic ambers are based on labdanoid diterpenes with regular configurations, which are including communic acid, communol and biformenes. The price of raw Baltic ambers fluctuates wildly for several reasons. Therefore thermal optimization products of Baltic ambers have emerged in the market for many years. The huge price difference and collection value difference between natural Baltic ambers and thermally optimized Baltic ambers have already caused alarm to Chinese consumers. The research object is a representative Baltic amber chunk with wax-like appearance, which was cut into two sets of the same size, 6 pieces of each set. Thermally optimized Baltic amber samples (Jin Bao-mi, Jin Po, Hua Po, Xue Po, Lao Mi-la, Bai La) of one set was obtained under multiple experimental conditions, in addition, two samples in this set were further sectioned and heat-treated in the second stage. Through the infrared spectrum analysis, the spectral characteristics of thermally optimized Baltic ambers were obtained which can be used as the differential basis on distinguishing natural Baltic ambers and thermally optimized Baltic ambers. The results showed that thermally optimized Baltic amber samples in nitrogen or oxygen environment underwent polymerization and esterification reactions, and thermally optimized Baltic amber samples in acidulous aqueous solution underwent polymerization and hydrolysis reactions. Using formula Ratio(I1)=ACarboxylic acid carbonyl CO stretching vibration 1 710 cm-1/AC—H unsymmetric bending vibration 1 456 cm-1to determine whether the Baltic amber has been thermally optimized is very persuasive. This method is applicable to the identification of Jin Bao-mi, Jin Po, Hua Po, Xue Po and Lao Mi-la. When I1≥1, the Baltic amber samples are not thermally optimized. When I1＜1, the Baltic amber samples are thermally optimized. As an added note, this criterion should not be used to Bai La. Raman spectrum results also show that the maturities of thermally optimized Baltic ambers are increased in different degrees. The maturities from high to low are Lao Mi-la, Xue Po, Hua Po, Jin Po, Bai La, Jin Bao-mi. This research aims to provide a scientific basis for identifying thermally optimized Baltic ambers, improving the utilization rate of Baltic amber raw chunks and developing the preventive protection technology for the Baltic amber museums.
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