Readers may be interested in this lecture at the Siam Society on 20 August 2020 by Pira Venunan of Silpakorn University. Registration recommended becauseof social distancing requirements.
Laterite, though considered low-grade, has long been nominated as a potential iron ore source in lower Northeast Thailand, an area devoid of large iron ore deposits. The procurement of this particular geological material and iron production are viewed as one of the crucial reasons for an expansion of settlements which had driven the social development in the region in both later prehistory (BC 500 – AD 500) and early Angkorian Khmer period (9th – 11th century). This technical proposition, however, has never been evaluated systematically through the perspective of archaeometallurgy. To tackle this issue, over 150 samples of metallurgical remains recovered archaeologically in Ban Kruat were subjected to microstructural and chemical analysis, providing an opportunity to scrutinise how iron was extracted and what adjustment and strategy were needed to achieve the desired metal. The analytical results illustrated a promising picture of laterite being exploited for iron. This involved the smelting of locally available alumina-rich laterite nodules, despite their variable iron contents, inside shaft furnaces under unusually high temperatures and reducing atmospheres, possibly resulting in the direct production of carbon-rich iron. Comparing with different workshops in Ban Kruat, the analysis saw very similar smelting practices being embraced, which may have been critically constrained by the ore chemistry. This rendered the technology rather resistant to change or improvement, notwithstanding the profound political or socioeconomic changes taking place concurrently in the region. (Presentation based on a journal article published by Dr Pira Venunan, Prof Marcos Martinón-Torres, Dr T.O. Pryce and Khun Borisut Boripon).