Negative-Muon Depth Profiling Reveals Near-Surface Gold Enrichment in Historical Shachihoko Scales from Nagoya Castle
Abstract
Surviving fish-scale plates from the golden shachihoko (Kin-shachi) ornaments of Nagoya Castle are rare historical gold–silver (Au–Ag) materials. Recent X-ray fluorescence (XRF) analysis and color measurements indicated a discrepancy between the bulk Au concentration and the visible golden appearance. To clarify the origin of this discrepancy, we applied negative-muon depth profiling to seven surviving Kin-shachi scales. Five samples exhibited Au enrichment from the interior toward the surface; deeper regions showed lower and nearly constant Au concentrations consistent with previous XRF results. These findings suggest near-surface Au enrichment resulting from an intentional surface treatment to enhance the golden appearance of Kin-shachi.
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Authors: M. Tampo, Takahiko Kutsuna, Misako Asahi, Masashi Sakai, Keisuke Murakami, Keitaro Nihashi, Izumi Umegaki, Soshi Takeshita, Shogo Doiuchi, Akiko Hashimoto, Souta Suzuki, K. Shimomura, Yasuhiro Miyake
Institutions: Nagoya University, High Energy Accelerator Research Organization, The Graduate University for Advanced Studies, SOKENDAI, Japan Proton Accelerator Research Complex, National Museum of Nature and Science