oa Iron Age Metal Distribution Across the Arabian Peninsula: First Results

The Arabian Peninsula has a wide variety of copper ore deposits that are distributed throughout the whole territory, with a particular concentration in the southeastern region, in what is modern day Oman. These resources, exploited since ancient times, are characterised by specific chemical and geological signatures that, when processed, give metals with distinctive compositions.

The Bronze Age (ranging from c 6,000 to c 3,000 years ago) was a period of major mining of copper deposits in this region, but very little is known about how this exploitation continued and changed during the Iron Age, starting c 3,000 years ago. The lack of published data on this subject is the basis of our research project “Iron Age Metal Production in the Arabian Region and in the Levant: A Comparative Study”, funded by QNRF and conducted at UCL Qatar. This is a lab-based project that examines ancient metal artefacts and metal production waste with the aim of shedding light onto the kinds of resources and level of technology employed at the time.

To date, investigations have been carried out on materials collected at three key Iron Age sites in Arabia, namely Tayma (Tabuk, KSA), Qattarah (Al Ain, UAE) and Salut (Nizwa, Oman). A great part of the materials analysed are made of a copper alloy characterised by a peculiar chemical signature, with variable amounts of arsenic (As) and tin (Sn) being jointly present in the low percentage range. Nevertheless, none of these samples has a tin content high enough to consider it a proper bronze. This is unusual for the type of metal composition that would have been expected in the Iron Age when the tin content in bronzes in other geographical areas was significantly higher, typically reaching from around 7 wt% in Egypt to more than 10 wt% in Mesopotamia and the Mediterranean world.

The high levels of variability of arsenic and tin detected in those materials lead us to consider whether this metal was the result of recycling operations. However, this required further investigation, so lead isotope analysis was used to try to establish the provenance of this group of finds. The results of these analyses show a good match for most of the As-Sn-containing copper artefacts in terms of isotopic signature, suggesting that they are likely to have the same provenance. This provenance can safely be identified as being in Oman, although the specific mining district has yet to be determined with certainty. The mining district of Yanqul is a likely source because an important Iron Age copper smelting site, Raki, has previously been identified in the area. Further detailed analysis of slag and other finds from Raki is still ongoing in order to test whether this is a possible origin for the metal identified in these sites.

It is interesting to note that groups of materials from different sites have been found to have the same geological ‘signature’ and hence provenance. This suggests that we are not dealing with recycled material but with a natural alloy that is the result of the processing of a specific copper ore, which is rich in arsenic and tin. The presence of this alloy in sites that are geographically remote from each other, suggests that it was traded over substantial distances across the region and must have played an important role in the overall supply of Arabia with copper.

The oasis settlement of Qattarah on the border between the UAE and Oman is of particular interest because excavations there yielded copper smelting slags, without any natural copper deposits being present in the area. Of particular importance is the observation that the metal prills analysed from those slags presented a similar distinctive As-Sn-enriched composition to the metal objects, a similarity that has been confirmed by lead isotope analysis. This means that not only the metal extracted from those specific ores was traded but also the ore itself; most likely because of the need for fuel which was available in the oasis settlements but not at the arid mine sites. These findings, however, do not explain why the natural alloy was traded long distances across the region.

It is unknown whether these ores were traded because their composition yielded a metal of particular quality, such as ease of melting and casting, or because it gave the metal a lighter and shinier colour compared to pure copper with its dull red tone, making the objects more attractive or ornamental. It is also possible that these ores were simply more easily accessible.

Further research on the project is ongoing and it is hoped that future analysis of samples from other contemporary sites will better our understanding of how widespread the use of this specific alloy was and the rational for the trade.

The research presented here was made possible by NPRP grant 6-813-6-016 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The academic generosity of our project partners in the mentioned case studies is also gratefully acknowledged.