Characterisation of silver surface enrichment in historical silver coins — a method proposal and study of the trace element behaviour

Activity: Talk or presentation typesLecture and oral contribution

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Mahir Hrnjic - Lecturer

The depletion of Cu from near-surface areas is a common issue in the non-destructive analysis of historical silver coins. Such coins will exhibit higher content of Ag near a surface of a coin, which might lead to the misinterpretation of a coin’s original composition. The study evaluates previously reported non-destructive method for characterising Ag enriched surfaces on coins based on measuring and comparing the intensity ratios of Ag Kα/Ag Lα peaks between coins and Ag standards with a similar composition. A number of silver coins with different chronologies and origins were analysed with μXRF in order to measure Ag Kα/Ag Lα intensity ratios and subsequently compared with the peak ratios of Ag alloy standards with a different composition. In cases where silver surface enrichment was confirmed, coins were sampled and analysed with LA-ICP-MS to measure the content of trace elements in the core and at the surface of coins. The analysis confirmed that the presence of silver surface enrichment was not detected with all Ag silver standards and that multi-standard approach allows for more reliable identification. The results from LA-ICP-MS show that besides Ag and Cu, the silver surface enrichment also influences behaviour of minor and trace elements — Au, Co, Ni, As, Rh, Pt. The content of Au was significantly higher in the enriched areas comparing to the core of coins; while Co, Ni, As, Rh, Pt were depleted from the surface. The study suggests the application of multi-standard approach in identifying the silver surface enrichment in fineness and provenance studies of historical silver coins.
9 Apr 2019

Research field group

NameSchool of Culture and Society - Centre for Urban Network Evolutions (UrbNet)
Date03/02/2015 → …
LocationMoesgård Allé 20

ID: 149941790