An Archaeometric Investigation of Gems and Glass Beads Decorating the Double-Arm Reliquary Cross from Liège, Belgium

In 1914, a magnificent reliquary cross dating from the early XIIIth century was discovered in a safe from the Liège Cathedral. This double-arm cross shows a wooden structure, covered by gold-coated copper on the front, and by carved silver plates on the back. Its total length is 34 cm, and it is covered by filigrees, gems, glass beads, and pearls on its front. The reliquary cross was analysed by Raman spectrometry and X-ray fluorescence spectrometry (pXRF) to determine the mineralogical and chemical compositions of gems, glass beads, and metals that have been used to decorate it. The results confirm the identification of twenty-five turquoises from Egypt, one garnet from Sri Lanka, as well as six quartz and one opal whose origin is difficult to certify. Twelve glass beads, showing green, blue, or amber tints, were also identified. Their compositions either correspond to soda lime glasses with natron or to potash–lead glasses similar to those of Central Europe. Moreover, a small polished red cross and a green stone appear to be constituted by nice doublets, composed of coloured glass covered by quartz. The filigrees contain Au and Cu, while carved plates covering the edges and the back of the cross are made of silver.