Application example: The Servatius reliquary of the Quedlinburg cathedral treasury

The Quedlinburg cathedral treasury is home to the reliquary of St. Servatius, which once contained the relics of 19 Christian saints. The ivory reliefs show Jesus and 11 of the apostles with their attributes, surrounded by columns with decorative capitals. They are partly gilded and are framed by an ornate golden fitting with jewel inlays. Stylistic considerations lead to the conclusion that the reliquary was elaborated and modified over several centuries, beginning with a gemstone from the early Roman imperial period and ending with the gold fitting from the 12th century AD.

The ion beam analysis method of PIXE (proton-induced X-ray emission) yielded further valuable information by non-destructive examination of chemical composition. It showed that the functionally different gold components – i.e. the fitting, the gildings, and the decorations on column capitals  – also differ in their chemical composition. The fitting showed the lowest content of added silver and copper, while the gildings contained more silver and the capital decorations contained more copper. The composition of the gildings agrees with that of a small gold inlay; other inlays had been broken out, however. Thus, gildings and inlays could have been manufactured simultaneously during the initial elaboration of the ivory plates, or alternatively some of the inlays could later have been reworked into gildings. The different chemical compositions of the fitting and the capital decorations suggest that these components were added to the object at later times.

Inspections with a light microscope had also shown indications that numerous ornamental gold inlays had been removed mechanically in modification of the original design. PIXE measurements confirmed the presence of residues of gold as well as of the material of tools used for removing the gold inlays. The inlays were made from very pure gold, which possesses the ductility required for this manufacturing process. By checking for the presence of gold residues in various locations on the reliquary, the original design was revealed.

In summary, the PIXE investigation of the gold composition support the conclusions on the sequence of modifications of the reliquary. Moreover, the localization of smallest gold residues on the reliquary enables the reconstruction of its original design.

• C.Wendt and C. Neelmeijer, Das Servatius-Reliquienkästchen aus dem Quedlinburger Schatz.
  Restauro 2/1993