„Non-invasive analyses of the gold alloys and the precious stones of the so-called Gisela tresury“ (Mayence/Wiesbaden, end of the 10th c.) from the Kunstgewerbemuseum der Staatlichen Museen zu Berlin by means of synchrotron XRF and portable Raman spectroscopy
The gold treasury, which was named after the empress Gisela (984/85-1060), is one of the most famous set of jewellery from the central Europe dating from the 11e s. The ensemble was discovered in several finds between 1880 and 1887 in Mayence and Wiesbaden. Today a large part of the treasury is kept by the Kunstgewerbemuseum Staatliche Museen of Berlin (KGM). This set bears 24 objects acquired by the Duc Max von Heyl in Darmstadt (Germany) in 1912. From the 24 objects four rings disappeared during the Second World War. The main corpus could be rescued, slightly damaged however, due to fortunate circumstances.
This ensemble has been scientifically studied by Otto von Falke in 1913 and Mechthild Schulze-Dörrlamm in 1991. In 1999 new discoveries have been made by Antje Krug while studying again the objects. They are now not considered any more as a homogeneous discovery but as a compilation of pieces during the 19th century. A fine goldsmith study in 2009 by Jochem Wolters is in agreement with the latest discoveries. It is now necessary to confirm these microscopic observations of different parts of the treasury by more objective investigations. Therefore, an interdisciplinary research program has been conceived with Lothar Lambacher, curator at the KGM, involving completely non-destructive analytical methods with a microscopic resolution in order to better identify, first, stone and others inlays and second, gold material used for different parts of the treasury.
The different parts of the gold objects, especially the soldered parts, were analyzed using synchrotron X-ray fluorescence analyses at the BAMline, BESSY II, HZB, Berlin. The analytical results have been exploited in a qualitative and in a quantitative way. A statistical data evaluation using Principal Component analysis (PCA) of the gold data allowed the separation of the gold alloys in different groups, which have now to be attributed to different parts of the treasury, in order to differentiate the original pieces from added ones. The numerous inlays made of precious stones have been examined using microscopic observations and a portable Raman analytical device. These results allow new insights into medieval goldsmith techniques and precious stone decorations of excellent quality.
Partners: BAM, BESSY II/HZB, C2RMF Paris
Duration: 2011 to 2016