The Effect of Accelerated Alteration on the Discrimination between Baltic and Romanian Amber

Abstract

Ten geological samples (five from each source-Romanian amber and Baltic amber) in duplicate for five different media (air, water, saline, acid and basic) were subjected to thermal alteration at 80 1 2°C for 12 weeks, in the dark. The samples were analysed before and after the accelerated alteration experiment by Fourier transform infrared spectroscopy, both in transmittance and reflectance mode, and the acquired spectra were statistically processed by multivariate data analysis, mainly using principal component analysis. The results of the experiment are useful in giving a better picture of how to discriminate between archaeological amber artefacts.

Fourier Transform Raman and Statistical Analysis of Thermally Altered Samples of Amber

“…We can emphasize that the results of the statistical analysis applied on Raman data are similar to those on FT-IR-reflectance data previously reported; 27 however, they are more clear and convincing having the advantage that Raman data were used for statistical analysis without additional treatment compared with FT-IR data. 40 We can conclude that this optimized Raman technique (laser 1064 nm, power on sample ∼190 mW, and 2000 scans per sample) coupled with statistical analysis represent a promising set of tools for amber artifacts analysis.…”

“…The strong separation of the results for altered Romanian amber samples is not something new. 27 PC3 was chosen instead of PC2 because it provides a closer location for the duplicates (see the arrows from Fig. 4), although PC3 accounts for less than 1% from all the processed data.…”

“…Studies on accelerated alteration and specific changes that occur on altered matter, such as archeological amber, were previously published but focused on conservation issues within the repositories of the museum. 13,27–31 It was also suggested in the specialist literature that chemometrics techniques could be applied with the advantage of improving the spectral recognition from the background interference. 19,25,27,32…”

“…These data were in accordance with the FT-IR data already published in a dedicated journal. 27 To our knowledge, no Raman survey was conducted on these two types of amber (Baltic and Romanian) for this purpose.…”

Examination of amber and related materials by NMR spectroscopy

“…More sophisticated vibrational methods have been applied, but the Beck criteria have not been supplanted. The MS analysis of Baltic and Romanian ambers was reported as early as 1970, and phenomenological criteria based on the presence of particular peaks attempted to distinguish geological sources . More comprehensive and useful studies using MS in conjunction with pyrolysis GC did not begin until the 1990s .…”