The Preuschdorf coin hoard: determination of the alloy composition by combination of PIXE and RBS

Lucile Beck1,
Elise Alloin2
U. Klein3
C. Berthier4
1C2RMF, Palais du Louvre, Paris, France
2Pôle d'Archéologie Interdépartemental Rhénan, Sélestat, France
3Landesmuseum Württemberg, Stuttgart, Germany
3UESMS - Institut National des Sciences et Techniques Nucléaires, Gif-sur-Yvette Cedex, France

The Hoard of Preuschdorf was recently found in Alsace (France). It consists of 7270 silver coins, which were probably buried during the Thirty Years' War (1618-1648). The importance of this find is not only due to the number of coins but also due to the large variety of production in terms of mints as well as in terms of time scale. The coins were struck from the end of the 15th century to the beginning of the 17th and come from cities located in present day East France, Germany and Switzerland. The study will present the first results concerning the characterization of the coin alloy. The alloy composition was determined by ion beam analysis techniques combining Particle Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS) in order to accurately measure the coin fineness. PIXE gives access to the elemental composition whereas RBS is used for checking the sample homogeneity. The first results have shown that the coins are mostly composed of a silver-copper alloy with a silver content ranging from 25 to 42 %. In addition of these homogeneous coins, the study has identified several coins composed of a copper core with a silvered surface, suggesting the presence of counterfeit coins. The analyses revealed that different silvering processes had been employed. One of them was characterized by the presence of mercury, indicating the use of the amalgam silvering technique.