BACKGROUNDBlue amber is mainly produced in the Dominican Republic, Mexico and Myanmar. Generally speaking, the formation mechanism, composition and spectral characteristics of blue amber are closely related to its specific geographical environment. Therefore, the study on the origin of blue amber has become a hot topic in the field of gemology, archaeology and biological mineralogy, and the origin of geographical districts of blue amber has become a hot research topic. Previous studies mainly used infrared spectroscopy, X-ray fluorescence spectroscopy, mass spectrometry, and isotope tracing to carry out a relatively systematic study on the origin of blue amber, but were limited to the similarity of blue amber, and the spectral characteristics of blue amber from different origins showing similarities. Due to the low popularity of the application of some detection devices, the application of the detection method based on the above-mentioned corresponding devices is greatly limited.
OBJECTIVESTo identify photoluminescence (PL), Raman spectroscopy and trace element characteristics of blue amber with different origins.
METHODSPhotoluminescence and Raman spectroscopy combined with trace element analysis were used to study the spectral and elemental occurrence characteristics of blue amber from Dominican Republic and Mexico.
RESULTSThe results showed that: (1)At room temperature, using PL spectrum with 405nm as the excitation wavelength, the peaks at 450, 475 and 502nm appeared simultaneously for blue amber from Dominican Republic. In contrast, there was no significant characteristic peak in Mexican blue amber. The differences in PL spectrum of blue amber from the two origins can be used as a direct basis for the traceability and identification of its origin. (2)Using the Raman spectrum with 785nm as the excitation wavelength, the Raman peaks of blue amber from Dominican Republic at about 154, 468, 901, 1177 and 1312cm-1 were more prominent or sharper than those from Mexico. The ratio of the peak intensity at 1653 and 1446cm-1 (N=I1653/I1446) in the corresponding spectrum of the amber from Dominican Republic was significantly higher than that from Mexico. (3)Trace elements of S, Si, Fe and Cu were present in the blue amber from the two regions, and the content was S>Si>Fe>Cu. The content of Cu in blue amber from Dominican Republic was generally higher than that from Mexico. Therefore, the occurrence and content characteristics of Cu can be used as one of the evidences for the traceability of Dominican blue amber.
CONCLUSIONSThe research work provides theoretical and technical support for the origin of blue amber with different geographical locations. It can also provide a salutary reference for identification of the geographical location for other gems.