Microchemical surface analysis of two Numidian coins

This work is a contribution to the microchemical surface analysis of two Numidian coins. Numidia was an ancient kingdom of northern Algeria during 2nd and 1st century BC. Investigations were performed with scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS), energy dispersive X-ray fluorescence spectrometry (EDXRF) and X-ray diffraction (XRD). The identification of the coins was done thanks to the name initials and effigy of King Massinissa. SEM observations of coins showed heterogeneous surfaces. SEM and EDXRF analyses showed an alloy structure with copper (65%), antimony (19%) and lead (16%). The XRD identified a metal structure and corrosion products which were on the coin surfaces: Litharge (PbO), Hydrocerussite (Pb3(CO3)2(OH)2), Bindheimite (Pb2Sb2O7) and Bystromite (MgSb2O6).

Highlights► Microchemical surface of two Numidian coins were studied. ► Photographs, scanning electron microscopy coupled with the energy dispersive spectrometry, the energy dispersive X-ray fluorescence spectrometry and X-ray diffraction were used. ► Three basic metals Cu, Sb and Pb were detected and analyzed. ► The corrosion products litharge (PbO), hydrocerussite (Pb3(CO3)2(OH)2), bindheimite (Pb2Sb2O7) and bystromite (MgSb2O6) were identified on the coin's surfaces.