Island Southeast Asia and ancient glass exchange: Insights from jar burial sites in Bacong, central Philippines

Abstract

Much remains unknown about the participation of Philippine social groups in ancient glass trade during the period known in the Philippines as the “Metal Age” (ca. 500 BCE – 1000 CE). This study hopes to address the poor understanding of ancient glass exchange in the Philippines through the examination of glass beads recovered from the Bacong region jar burials in Central Philippines. Elemental analysis using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is utilized to address questions on compositional similarity of Bacong glass beads with glass beads from South and Southeast Asia and identify networks of exchange Bacong communities took part in. Compositional analysis determines that there are four types of glass found in Bacong including mineral soda-high alumina glass (m-Na-Al), mineral soda glass with moderate lime and alumina concentrations (m-Na-Ca-Al), soda plant ash and lime silica glass (v-Na-Ca) and potash (K) glass. Additionally, the Sr and Nd isotope signatures of two m-Na-Al 1 and two m-Na-Ca-Al beads were measured in an attempt to elucidate more precisely their provenance. The isotope results study determines that these glass beads are likely sourced from Sri Lanka and South India reflecting maritime exchange between island Southeast Asian communities with South Asia possibly in the early to mid-first millennium CE.