An archaeometallurgical study of iron production in Ban Kruat, lower Northeast Thailand: technology and social development from the Iron Age to the Imperial Angkorian Khmer (fifth century BC - fifteenth century AD)

Iron has long been regarded as a crucial element facilitating at least two key activities at the centre of the economic and political history of lower Northeast Thailand from the Iron Age (500BC-AD500) to the fall of Angkor in AD1453: agriculture and construction of water conservation. Both sectors are thought to have been mechanisms manipulated by local and regional elites to generate and maintain wealth and power. Building upon this claim, iron production may have also had a major socioeconomic role in society. However, despite many side references to the abundance of iron-related remains in the archaeological record, little is known about the primary production of iron and its spatial distribution in this region, and the evidence has rarely been explored to its full potential to construct arguments from a technological and craft production point of view. To better our understanding of this industry and its role in the broader cultural landscape of lower Northeast Thailand, this thesis focused on iron production remains. Slag, technical ceramics, and laterite fragments (possible ore) found at slag deposits in Ban Kruat in Buriram province, and broadly dated from the Iron Age to the Angkorian Khmer period, were analysed. The aims were to reconstruct the chaîne opératoire of Ban Kruat ironmaking technology, and to use these technical with broader archaeological and historical knowledge to discuss the environmental and social embeddedness of iron and iron making in the regional setting of lower Northeast Thailand. Archaeometallurgical approaches were employed to extract relevant data from the finds, which were then discussed in social terms with the aid of conceptual frameworks from the social construction of technology and craft production. The results indicate that the whole production landscape was built upon very similar ironmaking practices, resulting in very comparable production waste and debris. The said process involved the smelting of locally available iron and alumina-rich laterite ores inside shaft furnaces under unusually high temperatures and reducing atmospheres, possibly leading to the direct production of carbon-rich iron. The low technical variability of this practice may have been critically constrained by the ore chemistry that forced the smelting practice to be formulated in such a way in order to win metallic iron from the peculiar ore available. This rendered this technology rather resistant to change or improvement, in spite of the profound changes taking place concurrently in lower Northeast Thailand, ranging from the political (chiefdoms, early state, and the empire) to the socioeconomic (community-based specialised production to Angkorian temple-based economic system)

Bullion production in imperial China and its significance for sulphide ore smelting world-wide

Gold and silver production was of major importance for almost all ancient societies but has been rarely studied archaeologically. Here we present a reconstruction of a previously undocumented technology used to recover gold, silver and lead at the site of Baojia in Jiangxi province, China dated between the 7th and 13th centuries AD. Smelting a mixture of sulphidic and gossan ores in a relatively low temperature furnace under mildly reducing conditions, the process involved the use of metallic iron to reduce lead sulphide to lead metal, which acted as the collector of the precious metals. An experimental reconstruction provides essential information, demonstrating both the significant influence of sulphur on the silicate slag system, and that iron reduction smelting of lead can be carried out at a relatively low temperature. These new findings are relevant for further studies of lead and precious metal smelting slags world-wide. The technological choices of ancient smelters at this site are then discussed in their specific geographical and social-economic settings