Investigation on Structure of Potsherds from Sirvan Historical Site according to XRF and XRD Analysis

According to experts, Sirvan historical site in Ilam province belongs to the Sassanid period or the early Islamic centuries. Despite the archaeological importance of this site, unfortunately, methodical and broad archaeological and archaeometical activities have not been performed. To the systematic investigation of samples obtained from the initial excavations for geoarchaeological studies, 14 potsherds from this site were examined. Concerning this question that what are the main geochemical properties, structural similarities, and differences between these specimens, experimental analysis was done. In order to the elemental and mineralogical description of samples, estimating their firing temperature, and preparing a model for classification of them, chemical composition and mineralogical phases of samples were characterized through X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis. The standard deviations of the amount of silicon, aluminum, iron, calcium, and magnesium oxides were calculated at 11.527, 3.290, 2.705, 5.887, and 2.087, respectively. High dispersion of the quantity of elements especially for Si and Ca reveals that these samples belong to different workshops, regions, or historical periods with variation in sources and amounts of raw materials and processing steps. in the same geographical area. Moreover, any special model for classification of samples not found, except samples no. S8 and S9 that have similarity in their chemical and mineralogical composition. In addition, the three samples S12, S13, and S14 have completely different chemical and mineralogical characterization and are probably to be imported products. Also in samples with a high amount of the calcium oxide (more than 6%), probably local limestones were used as temper. In general, these samples can be considered as local production (except for the three examples mentioned. Concerning not identifying the clay minerals and presence of calcite (likely primary), diopside, and gehlenite (as firing products), the firing temperature of these samples was estimated between 850 - 900.