New Perspectives on Prehistoric Workshop Traditions in Central Thailand: A Case Study of Stone Ornament Drilling Methods

In SPAFA’s SESH on 16 August 2022, we literally drilled down into details with Drs Thanik Lertcharnrit (Silpakorn University) and Wannaporn Rienjang (Thammasat University), talking about stone beads found at the Phromtin Tai site in Lopburi province, Thailand. Their presentations are based on an upcoming paper jointly authored with Alison Carter (University of Oregon), Jonathan Mark Kenoyer (University of Oregon) and Randall W. Law (University of Oregon). The SESH was moderated by Dr Noel Hidalgo Tan, SEAMEO SPAFA’s Senior Specialist in Archaeology.

Dr. Thanik set the stage by introducing the site of Phromtin Tai in Lopburi province, where excavations were carried out between 2004-2019. Radiocarbon dates from the site indicate major periods of occupation between 500 BCE – 300 CE, from the end of the Iron Age to early Dvaravati period. At Phromtin Tai, archaeological evidence suggests that the ancient people there had various levels of subsistence and industry, including hunting, gathering and fishing, rice and millet farming, copper production and ornament working.

The main focus of the SESH was on the ornaments found in Phromtin Tai, and stone ornaments of various materials, shapes and sizes were found at the, both within and outside of burial context. Compositional analysis of the stone beads suggested an origin from the Deccan region of West India, indicating trade networks reaching as far as India and Afghanistan.

Dr. Wannaporn presented an analysis of a sample of 57 beads and identified three types of drilling methods: using a diamond tipped drill bit, a metal bit with abrasives, and the possible use of stone drill in some cases. Different methods left behind different physical signatures of the finished products. She also presented some ethnographic examples from India of how beads were drilled.

The identification of the three drilling methods are closely associated with the type of material being drilled, or may also indicate the presence of different workshop traditions expressed through the Phromtin Tai beads. Diamond-tipped bits were used on on carnelian and agate beads, while metal bits were used on softer stone such as nephrite Most interestingly, some of the agate pendants and carnelian beads from Phromtin Tai shows signs of being drilled with a diamond tipped drill, but have other physical characteristics that are only found in Phromtin Tai. Thus, the possibility of a local drilling adaptation was raised.

A short question and answer session followed about the beads discussed and the associated technologies, such as whether or not the strings were found in association with the beads, and the types of metal used for the beads.