Macroscopic and microscopic characteristics of Pictograph of Kuhdasht in Sarsarkhon mountains of Lorestan province

Pictographs of Lorestan province in Kuhdasht city are one of central Zagros' most prominent and important cultural works. The paintings of this region have not been studied from an experimental point of view. Considering the use of colors and their importance in Iranian art, these colors were sampled in a tiny amount, considering the principle of no visual damage. To achieve the research goal, laboratory methods have been used to identify the color substrate and pigments. In this research, three pigments, red, black, and orange, have been investigated by petrographic and FT-IR methods. In the method of thin section petrography and device analysis with James Swift model polarizing microscope, aiming to determine the bed and type of rock, Fourier transform infrared spectrometer (FT-IR) was used to identify the type of pigment. The archeological investigations on the colored pieces show that the type of pigments used to make the motifs were completely mineral, and no organic pigments were found. Microscopic images of the sections of the paint layer show that these pigments were applied directly on the rock, and as a result, there was no substrate. Therefore, the pigments used to draw motifs are a mineral structure and a combination of iron; where the natural red pigment of the earth, depending on the iron oxide chromophores and the presence of other minerals, can create orange tones to red and black shades, which can be seen as increasing or decreasing the type of iron oxide. Finally, considering that the structure of the colors was in the form of mineral compounds, it can be acknowledged that this structure is one of the most important reasons for their durability.