Geologic provenience analysis of agate and carnelian beads using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS): A case study from Iron Age Cambodia and Thailand

Agate and carnelian beads, imported from South Asia, were widely exchanged in Southeast Asia during the Iron Age period (500 BCE-500 CE). Recent studies have identified changes in bead types and manufacturing methods over time, as well as evidence for possible local production. In order to understand the broader implications of these developments, geochemical analysis using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was undertaken on 73 beads from 10 Iron Age sites in Cambodia and Thailand and 64 geologic samples from four sites in India, Iran, and Thailand. The results show that many of the beads were produced from raw material derived from the Deccan Traps, India and that there is not yet strong evidence for bead production using a Southeast Asian source. Secondly, we find that there is not yet clear evidence for a change in the different geologic sources used to produce beads over time. This study adds to the growing body of literature highlighting the utility of LA-ICP-MS in differentiating and assigning provenience to agate/carnelian and other silicates.