Lead–barium glass production in North China during the Warring States period — Scientific study of square eye beads from a Qin tomb in Xianyang, Shaanxi

This study presents a scientific analysis of the special square eye beads excavated from a Qin Tomb during the Warring States in Shaanxi province. The results show that all of the beads are composed of lead-barium glass, with low-impurity quartz sand, lead ore, and barium ore (Ba and Na content are positively correlated) serving as the raw materials; all appear to have been made through a winding method with square moulds. Beads of different colours were likely made in the same place. The results of typology and lead isotope analyses indicate that the square eye beads were produced in the Qin Kingdom, demonstrating that, in addition to the Chu State, the more north-westerly Qin Kingdom was also able to produce lead–barium glass during this period. The positive correlation observed between sodium and barium contents should stimulate further study of the source of raw barium materials for lead–barium glass production and the relationship between lead–barium and soda–lime glass during this critical time in Chinese history.