Micro-CT-guided Analysis of Corrosion Morphology and Condition of Eastern Han Bronze Game Pieces from the Tushan Han Tomb, China

Two bronze game pieces from the Tushan Han Tomb, Xuzhou, China, were investigated to evaluate corrosion products, internal preservation state, and corrosion-related structural features using a minimally destructive, micro-CT-guided multi-analytical workflow. The objects derive from a well-documented Eastern Han context and offer a rare case for examining post-depositional alteration in small copper-based artefacts associated with an organic game-board assemblage. Raman spectroscopy identifies malachite, azurite, and cuprite as the principal corrosion products, while an additional yellow corrosion product remains mineralogically unassigned; the two specimens differ in corrosion thickness, continuity, and surface distribution. Specimen no. 2 preserves a thicker and more continuous altered outer zone than specimen no. 1, whereas X-radiography and repeat micro-CT examination indicate that its remaining metal core is structurally compact, without major cracks, voids, or extensive material loss. Because beam-hardening effects may affect CT contrast, grey-value variations were not used as direct indicators of mineral phases. Instead, micro-CT was used conservatively to assess altered-zone geometry, outer-zone continuity, and internal preservation, while phase identification was based primarily on Raman spectroscopy and supported by microscopic and cross-sectional observations. The inter-sample differences suggest localised burial microenvironmental variation, probably related to moisture conditions, ion migration, local soil chemistry, and contact with surrounding organic materials. This study demonstrates that a micro-CT-guided, conservation-oriented workflow can integrate non-destructive imaging, phase identification, and limited validation for the minimally destructive assessment of small archaeological copper-based artefacts.