Why Heating Pounamu (Jade) in Aotearoa New Zealand? Ethnography, Experimental Archaeology and Geomechanical Measurements

Anne-Claire Mauger1,2* and Natalia Seliutina1

Pounamu (jade) is a rare lithic material in the Pacific. In Aotearoa (New Zealand), pounamu remains the most significant cultural taonga (treasure) for the Māori, embodying mana (prestige), tradition, and spirituality. Although present in the archaeological record, pounamu artefacts belong to a lithic tradition that remains poorly documented. Recent doctoral research explored manufacturing techniques to reconstruct the chaînes opératoires of pounamu. A key discovery was the identification of heating as a primary technique in its manufacture, along with the addition of organic compounds. Traces of fire treatment found on archaeological artefacts were experimentally replicated, allowing for the identification of proxies to recognise heating in archaeological nephrite. Nephrite transformation was observed through changes in translucency, hardness, and colour tones. Geomechanical methods were used to measure the hardness and stiffness of the heated samples. The reduced modulus and Young's modulus were calculated using a Bruker TI Premier nanoindenter. These measurements revealed differing mechanical properties across heated samples. The benefits of heating pounamu are variously interpreted by traditional carvers who were consulted for this study. However, a review of ethnographic accounts suggests that the advantages of heating extend beyond material transformation and technical benefit. In this context, fire treatment encompasses a strong social and spiritual dimension, particularly when associated with other significant compounds.