Fig. 1. Chess pieces of Liubo uncovered from tomb of the Warring States in Shaanxi

Fig. 2. Micrographs of the sample surfaces
(a): Blue sample; (b): Purple sample

Fig. 3. Raman spectra of the samples
(a): Blue sample; (b): The weathering product of the blue sample surface; (c): The purple particle in the purple sample; (d): The blue particle in the purple sample

Fig. 4. Composition of the PbO and BaO in the samples

Fig. 5. Composition of the SiO₂ and CuO in the purple samples

Fig. 6. Compositon of the PbO and BaO of different lead-barium glass samples from different regions
red: Samples from Hubei; green: Samples from Chongqing; orange: Samples from Hunan; black: Blue samples of this work

Fig. 7. BSE-SEM image and EDS result of the Chinese Purple

Fig. 8. The reflectance spectra of the Chinese Purple samples