A Re-evaluation of inverse segregation in prehistoric As-Cu objects

This study revaluates reported cases of prehistoric As-Cu objects with ‘silvery surfaces’, which are usually interpreted as the result of inverse segregation. Further possible explanations for such surfaces, such as an arsenic-rich α-solid solution, cementation, or post-depositional precipitation, are discussed. The segregation of arsenic was studied in As-Cu ingots produced in chill cast moulds at several compositions, which underwent surface treatment with an NaCl solution. The microstructure and surfaces of the As-Cu alloys were analysed using optical microscopy and SEM-EDXS. Special note of out-of-equilibrium As-Cu phases are discussed, as well as a comparison of inverse segregation to all other means of achieving surface silvering. •Lists known instances of silvery surfaced prehistoric As-Cu objects.•Provides explanations for the possible causes of silvery surfaces such as: α-solid solution, cementation, or precipitation.•Provides microstructural and surface analyses of the As-Cu alloys via SEM-EDXS and optical microscopy.