Discussion on weathering products of copper barium silicate octagonal prism and related problems

The copper barium silicate octagonal prism unearthed from the Warring States to Qin periods is important evidence for synthetic violet materials in ancient China. However, studies have mainly focused on matrix composition and function, while weathering products and their formation mechanisms remain insufficiently explored. In this study, three octagonal prism samples from the Hejia cemetery in Xianyang, Shaanxi Province, were analyzed using ultra-depth microscopy (OM), SEM-EDS, and Raman spectroscopy. The results indicate that stable weathering products such as PbCO₃ and BaSO₄ are commonly formed on the prism surfaces. Under specific burial conditions, secondary minerals including Pb₅(PO₄)₃(OH), Pb₂Cu(PO₄)(SO₄)(OH), and CuPb(SO₄)(OH)₂ were also identified. Combined with density calculations, differences in density and weathering degree among samples suggest variations in production formula and firing process, with some samples showing material properties close to the lead-barium glass system.