Analytical chemistry for cultural heritage : material analysis of archaeological silver coins using X-ray based techniques

Abstract

This Ph.D. thesis is a result of two different interdisciplinary projects and concerns the scientific analysis of archaeological silver coins, dealing on one hand with early modern coinage of the Ottoman Empire of the 16th and 17th century and on the other hand with ancient Roman Imperial coinage of the Emperor Trajan (AD 98 - 117). µ-XRF, µ-SRXRF and µ-PIXE were applied in order to determine the silver contents as well as the minor and trace elements. The type of the alloy was investigated, as well as if coins minted in different locations demonstrated homogeneous traits concerning the predominant impurities (Au and Bi) which could suggest a common ore. Finally, SEM/EDX was applied in order to study the homogeneity/heterogeneity of the coins and the presence of surface enrichments.<br />Concerning the coins from the Ottoman Empire, in general the silver content of the analysed specimen varies between 90 and 95%. These outcomes have not supported the historical interpretations, which predict that during the period studied a debasement of approximately 44% of the silver content of the coins should have occurred.<br />Previous metallographic analyses done by several scholars on Roman Imperial coinage of Trajan had been inadequate to clarify the central numismatic and economic questions. With the presented analyses, it was possible to correct the results of the earlier research and to provide, for the first time, a secure basis of data for the investigation of the development of the silver alloy used for denarii in Trajan's reign.<br />