Our work has focused on 1) documenting the material - carried out through museum visits; 2) undertaking archaeometric analyses, of both reference material and Viking-Age silver (overall, we have generated new lead isotope and trace element data for 195 ninth-century coins (reference material), 99 items of archaeological lead from Viking-Age contexts, 297 ninth-century silver artefacts, in addition to 65 other analyses of earlier (7th- early 9th century) material), and 3) analysing the numismatic contents for chronological patterns.
For each artefact/ coin, we captured both lead isotope ratios and trace element data (in particular gold and bismuth) in order to characterize the silver and identify potential source(s). We developed an interpretive framework, taking into account silver recycling and cupellation (refining) (publication 2). The objective was to identify the relative amounts of eastern and western silver entering Scandinavia. We worked in labs across Europe (Fig. 1) and developed with colleagues a portable laser ablation system (Fig. 2) for minimally invasive sampling with high precision (publication 4).
Analysis of dirhams revealed they their silver derived from dry silver ores - not galena (publication 3), opening up the question of silver sources. From our analysis, we identified sources of mining across the Caliphate (publication 9) (Fig. 3). This also allowed us to develop an isotope fingerprint of dirham silver reaching Scandinavia (publication 5). We showed that there was a chemical difference between stocks of silver entering Scandinavia before and after 850 (Fig. 4). The pre-850 signature was especially strong in the analysed silver, showing that significant quantities of dirhams must have reached Scandinavia at this early date, but were melted down. Analysing Viking silver objects, we found a significant pre-850 Islamic component in all regions apart from the Irish Sea and on the Continent. The Vikings didn't just extract local silver, they also brought it with them. Western silver was visible, but not in the volume expected, suggesting that the impact of the Viking raids may have been exaggerated in written accounts. The Islamic connection was strong even early on in the ninth century, before dirhams are recorded in significant number.
Thanks to the flexibility of the ERC grant, we have been able to apply our methods and approaches to other, early medieval material. Our analysis of lead, undertaken initially to evaluation the evidence for cupellation, revealed new insights into lead mining. For instance, we found that lead was mined in the North Pennines in the Viking Age, and that this lead was shipped across the North Sea to Scandinavia (publication no. 11). We also looked at some earlier material: the earliest coins minted in post-Roman England and France, from the end of the seventh century. This work revealed, astonishingly, that the coins were initially made of Byzantine silver that was stored as plate in England (Fig. 6). In other words, the silver was present in England and a decision was made to liquidate it to turn it into coinage around c. 680. After that, silver from France was used to produce silver coins on both sides of the North Sea (publication no. 10). Investigating Scandinavia's eastern connection also encouraged us to look at metals from the early Iron Age site of Helgo on Lake Malaren, Sweden, a precursor to the famous Viking town of Birka. In analysing brass, copper and lead, we found evidence that brass was imported from the Byzantine Empire, as early as the fifth/ sixth century (publication no. 12).
