Microscopic and microanalytical study on Sasanian metal objects from Western Iran: A case study

Abstract

Recent archaeological excavation in western Iran discovered a Sasanian palace called Ghaleh Guri (Qela Gowri) beside of the Seimarreh River. As part of the archaeometric studies on the site, five metallic objects (a coin, a disc, a vessel, a decorated strip and some pieces with no specific function) were sampled and analysed using OM and SEM-EDS to determine alloy composition and microstructure. The results showed that strip is made of copper, disc, vessel and unidentifiable object are tin bronze and the coin is made of silver-copper alloy. Tin content in the vessel is about 30 wt% and may be classified as high-tin bronze. The microstructure of samples also revealed that the amount of working and the heat treatment was variable, most likely due to their different compositions. ARTICLE HISTORY

Metallurgical investigations of Indo-Sasanian Copper-Silver alloy coins of Gurjara-Pratiharas dynasty

“…%) in comparison to the dark phase (14 wt.%). These results are in good agreement with the earlier studies [10]. The copper-silver alloy phase diagram is shown in figure 6.…”

“…It has been observed that debased silver with different amounts of copper has been a metallurgical tradition to fabricate silver coins during the Sasanian period. Microstructural analysis of the silver-copper coin showed the casted structure with no additional working or minting [10]. However, a microstructural study of the sasanian silver coins indicates the evidence of mechanical operations along with annealing treatment as observed in other samples, which may suggest pre-heating of the primary silver before minting [9].…”

“…The high iron content in copper suggests the possibility of the use of unrefined copper. The general level of iron in the early copper or primitive copper (around 0.05%)is much the same everywhere, be it from Egypt, Britain, India, and the same is true of the enhanced levels associated with more advanced copper production where an average level of around 0.3% is fairly typical [10,16]. Thus, it may be understood that the iron might have entered in the copper during the smelting process.…”

“…The presence of gold in the silver coins indicated the use of non-galena ore for silver extraction, and microstructural analyses of samples pointed to the application of thermomechanical processes on coins [9]. The chemical composition and microstructure of the silver-copper coins were examined using SEM-EDS and optical microscopy [10]. The present investigation deals with Indo-Sasanian coins.…”

“…The typology, mint, denomination, and chemical composition of the Sasanian coins were studied under the project entitled "Sylloge Nummorum Sasanidarum" [5,6]. The chemical composition of the Sasanian silver coins was determined using various non-destructive techniques such as X-ray fluorescence (XRF), proton-induced X-ray emission (PIXE), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) [1][2][5][6][7][8][9][10], and percentage composition was used to explain the locations and identification of coin mines [1,8]. Mercury was observed on the surface of the silver coins of the emperor Khusro II (591-628) [7].…”