Many anaIytical methods have been used to identify the chemical composition of archaeological artefacts [1-4]. Museum CIRTA of the town of Constantine has a collection of more than 35000 coins and statuettes going back to Numide, Roman, Republican, Vandal and Byzantine times and is struck in the name of the cities, of the kingdoms and the empires. Surface analysis of these coins gives informations about the chemical composition and leads to recommendations for restoration and presevation. This work is a contribution of microchemical surface study of three coins with the effigy of the Numide King Massinissa (between 3rd and 2nd century before Jesus Christ). Scanning electron microscopy coupled with energy dispersive spectrometry (SEM + EDS) and energy dispersive fluorescence spectrometry (XRF) were used. The bulk of three coins is massif homogeneous metallic. Two coins are manufactured with lead (99.896% and 61.56%) and were probably conserved differently. The third one is from copper (92.28%). The optic microscopy (OMP) and SEM pictures of coins show heterogeneous surface with typical lead alteration products white patina of plumbonacrite, cerussite and hydrocerussite and red patina of cupric oxide on the cupric artefact. MS25 P09 Effects of Er 3+ and Yb 3+ doping on phase transitions of LiNH 4 SO 4 .
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