Non-destructive identification of surface enrichment and trace element fractionation in ancient silver coins

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A common issue in non-destructive surface analysis of historical silver coins is depletion of Cu from the near-surface areas, which in turn results in higher Ag content at a coin’s surface. This paper reports a non-destructive analytical strategy using µXRF for identification of Ag and Cu surface enrichments and depletions by comparing peak intensity ratios of Ag Kα/Ag Lα, Cu Kα/Ag Kα and Cu Lα/Ag Lα for coins and Ag-Cu standards of similar composition. Our characterization of coins from different contexts and chronologies shows that a multi-standard approach provides the most reliable identification of surface enrichment of Ag and depletion of Cu. Coins possessing Ag surface enrichment were further analysed with LA-ICP-MS to determine any differences in trace element composition between the cores and surface of the coins. We show that the near-surface regions of these coins are enriched in Au and depleted in Co, Ni, As, and Pt relative to their cores. These systematics allow for a more robust assessment of the degree of silver coin surface alteration critically important in measuring the original composition of historical silver coins.
Original languageEnglish
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume478
Pages (from-to)11-20
Number of pages10
ISSN0168-583X
DOIs
Publication statusPublished - Sep 2020

    Research areas

  • Silver coins, LA-ICP-MS, µXRF, Trace elements, Silver surface enrichment

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