Elemental profiling of 19th-century mosaics from Antoniadis palace, Alexandria, using LIBS validated by EDX

Abstract Laser-induced breakdown spectroscopy (LIBS) was employed to analyze the elemental composition of historical mosaic samples retrieved during the restoration of the main lobby in the Palace of Antoniadis Gardens, Alexandria, Egypt, dating back to the 1870s. A Q-switched Nd: YAG laser operating at 1064 nm with a pulse energy of 45 mJ was focused onto the surface of each sample, generating plasma under ambient atmospheric conditions. This approach enabled rapid, quasi-nondestructive analysis of the mosaic materials. Three distinct mosaic samples (red, black, and white) were examined. The LIBS spectra revealed the presence of key elements, including iron (Fe), calcium (Ca), magnesium (Mg), aluminum (Al), and silicon (Si), which are commonly associated with natural stones and ceramic materials. To validate the LIBS findings, energy-dispersive X-ray spectroscopy (EDX) was utilized as a complementary analytical technique. The comparison confirmed a pronounced correlation between the results of both methods, reinforcing the reliability of LIBS for cultural heritage studies. Additionally, comparative spectral analysis was conducted to identify the likely geological origins of the mosaic components. Spectrally, the black mosaic closely resembles basalt, the white mosaic resembles dolomite, and the red mosaic resembles pottery shards. These correlations suggest that locally sourced natural materials were employed in the production of the mosaics. This study highlights LIBS as a powerful tool for rapid, in situ archeological analysis, allowing for the efficient characterization and screening of cultural heritage objects without the need for prior sample preparation. Graphical abstract