Chemical and Microstructural Analysis of Some Achaemenian Silver Alloy Artefacts from Hamedan, Western Iran

Abstract

Precious metals have been often employed to manufacture various decorative artefacts at Pre-Islamic Iran. One of the most outstanding phenomena from this period of Iran was the extraordinary occurrence of the silver application to make various decorative objects. Indeed, application of silver and its alloys was extended for making different vessels and other decorative and royal objects in historic time, especially in Achaemenid (550-330 BC) and Sasanian (224-642 AD) Empires. In this paper, four silver artefacts dated to Achaemenid period, found in Hamedan region, Western Iran, are investigated to identify manufacturing/ shaping process as well as alloy composition. The examined objects consist of two bowls, one decorated plate and one decorated spoon with the head of a felidae. Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry (SEM-EDS) method has been applied on cross section samples to determine chemical composition of the alloys and the phases and optical microscopy (Metallography) and SEM techniques were used to study of microstructure and manufacturing/shaping procedure. The results showed that all samples were made of silver-copper alloys with different amount of copper in each artefact. Other elements have detected in minor/trace contents such as As, Pb, Cd, Al, S. The microstructure of samples showed interesting features that are related to manufacturing/shaping process to make silver artefacts and compositional aspects of the objects because of copper amount. In fact, two-phased microstructure could be observed in two Achaemenian silver bowls because of the high amount of copper in alloy composition. Two other artefacts include single phase microstructure depending on low content of copper in alloy composition.