Colour of the past in South Caucasus. The first archaeometric investigation on rock art and pigment residues from Georgia

This research is the first archaeometric investigation of Damirgaya and Trialeti painted rock art and pigments from grinding tools from the Neolithic settlement of Khramis Didi Gora, in South Caucasus, Georgia. The aims of this research are to characterise the rocks and pigments including identification of organic binder, as well as investigate the compatibility of inorganic pigments with locally available supplies and methods of production. Stylistic similarities and influences are compared with adjacent archaeological sites from Armenia and Azerbaijan, where traces of monochromatic red pigment were recovered in settlements, barrows and artefacts. Optical microscopy (OM) on loose samples and thin sections, X-ray powder diffraction (XRPD), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were used to determine the mineralogical and chemical composition of the samples. Employing micro-Fourier-transform infrared (μ-FTIR) and Raman spectroscopy, compounds were further characterized in both rock paintings and grinding tools. It was not possible to identify or ascertain the presence of binders, either because of their low concentration or complete molecular breakdown deterioration. From the pigment residues on both the rock art and grinding tools, hematite was the main colouring agent, with different associated minerals. For the rock samples, it was found that the rock art at Trialeti is on a dacite, whereas the one from Damirgaya is on a rock composed of quartz, with traces of iron oxides and phyllosilicates, suggesting that the rock originated from hydrothermal activity. The research presented here is the first chemical and mineralogical characterization of pigment residues and rock art from South Caucasian prehistory.