Geo-archaeological Mapping of Nephrite in Prehistoric Southeast Asia

IIZUKA Yoshiyuki1* and HUNG Hsiao-chun2

Nephrite (Ca-amphibole jade) is a tough rock with a dense, fibrous structure and an attractive colour, which has been widely used for polished stone tools and ornaments at least since the Neolithic in East Asia. High-quality, gem-grade nephrite is generally classified in two geological origins: serpentinite-related (S-type: actinolite-dominant) and dolomite-related (D-type: tremolite) nephrite. These sources are geographically restricted. Understanding the relationship between prehistoric nephrite-using cultures and their geological sources is therefore important for reconstructing regional exchange networks. Non-invasive analyses using low-vacuum SEM-EDS and on-site portable XRF have been applied to nephrite artefacts excavated from Taiwan and coastal areas of the South China Sea, including the Philippines, Malaysia, Vietnam, and Thailand. Comparison with a database of geological nephrite deposits in East and Southeast Asia indicates that many green-coloured (S-type) nephrite artefacts closely match the mineral chemistry of natural nephrite from eastern Taiwan, suggesting cultural connections between geographically distant regions. Recent surveys in Mainland Southeast Asia have further revealed that distinct types of S-type nephrite, different from Taiwan nephrite, were used in Myanmar, Thailand and Vietnam. In addition, the distribution of white-coloured (D-type) nephrite, whose geological source remains unknown, has been identified in several Mainland Southeast Asian contexts. This paper reports recent research results on nephrite artefacts in Southeast Asia and their implications for prehistoric exchange networks.