Mineralogical Evidence for Thermal Treatment of Nephrite Artifacts from Sanxingdui

Blackened and whitened surfaces are widely observed on nephrite artifacts excavated from the Sanxingdui sacrificial pits (c. 1200–1000 BCE) and have long been attributed to ritual burning based on archaeological observations. In this work, 206 nephrite relics were investigated, and controlled muffle furnace heating experiments on local modern nephrite were conducted to simulate the thermal alteration process. Most specimens experienced heating at 500–950 °C, resulting in surface darkening and decreased transparency. A small subset of jades underwent heating above 950 °C, triggering a mineral phase transition from tremolite to diopside, accompanied by whitening and structural loosening. This study provides physicochemical and mineralogical evidence of burning on Sanxingdui sacrificial jades. The crystal alteration data advance our understanding of ritual customs in ancient Shu culture and expand knowledge of prehistoric Chinese jade culture.