This research investigates the archaeometallurgical evidence for extractive copper metallurgy in Central Thailand. Samples were collected from ore sources, mounds of ancient slag, an excavated smelting site and from private collections. In addition to ore and slag, fragments of ceramic crucibles, often containing slag, were collected. Samples were taken from raw copper ingots and from the very few copper artefacts which were found. Mounds, which had been used for casting, were examined.

In order to determine the smelting processes used, metallurgical samples were examined by the following methods; visual examination; X-ray fluorescence spectroscopy (XRF), to determine the bulk chemical composition; reflected light microscopic examination of microstructures, to determine the mineralogical structure; electron probe microanalysis (EPMA), to determine the chemical composition of individual phases; and X-ray diffraction to determine the phase composition. Normative calculations and phase diagrams were used to calculate the theoretical mineral assemblages which would have resulted from equilibrium cooling.

Analysis showed that sulphide and oxide ores had been smelted and that ceramic crucibles had been used as reaction vessels. The smelting process was efficient, with only small amounts of copper remaining in the slag. the bulk of the copper was poured directly from the reaction vessels into ingot moulds and, in some cases, ingots contaminated with slag were produced.

There was no evidence of the use of tin at any of the sites investigated, and the thin copper artefacts which were found had been cast in unalloyed copper containing small quantities of arsenic.

This study has produced evidence of large scale copper production in the Lopburi area of Central Thailand. Differences in slag composition were observed between samples from a site at which there was no evidence of the use of iron, through Iron Age smelting sites, to a site where copper smelting continued to the 13th century AD.

It was concluded that the development of large scale copper smelting in the area, employing a technology not previously encountered elsewhere, related to a period in the first millennium BC when Centres associated with craft specialisation and intensified production appeared throughout Thailand.

Back to the PIA Introduction page

Back to the UCL home page