Change lost: Corrosion of Roman copper alloy coins in changing and variable burial environments

We studied the corrosion of Roman copper alloy coins that experienced alternations or progressive changes in their burial environment. used were still embedded soil a concretion selected from three professional excataved sites - Berlicum and Krommenie Netherlands Kempraten Switserland. mCT scanning neutron to record 3-D properties these prior (destructive) analyses. It proved possible tentatively identify coins. Microscope observations SEM-EDX analyses revealed complex processes, related changing environments. In horizon with fluctuating groundwater levels region upwelling reducing, iron-rich groundwater, gunmetal coin is essentially replaced by iron oxides while tin remains forms tin-oxide bands. Fluctuating redox conditions marine-influenced environments was shown transform copper-alloy into strongly laminated sulphides gypsum crystals, an outer surface copper-iron sulphides. Burial bronze charcoal rich layer probably caused temporary highly alkaline conditions. This most leach this coin, leaving behind tin-dominated mass, only limited amount (malachite) products remaining surrounding groundmass. all cases, processes tend be anisotropic, because cold-hammering during manufacture. Such on massive may produce features lead incorrect classification as subferrati, i.e. core. Our results help future distinguish corroded subferrati.