Multi-methodological Characterisation of Medieval to Early Modern Coral Beads from a Cesspit of the “Fronerei auf dem Schrangen” in Lübeck (Germany)

Abstract

Eight late medieval to early modern red beads representative of a total of 41 from a cesspit of the “Fronerei auf dem Schrangen” in  Lübeck, Germany, were investigated using micro X-ray computed tomography (3D-μXCT), X-ray microdiffraction (μ-XRD2), transmission electron microscopy (HRTEM) and Raman spectroscopy (RS). The microscopic properties of the material were characterised non- destructively or minimally invasively for colouration, mineralogical and chemical composition determination but also with regard to  their macroscopic external appearance. The polished beads are spherical with flattered tops and boreholes perpendicular to the  flattening and show partially traces of working. As base material for all examined beads, high Mg-Calcite with polyenes could be  identified. Combined with density and microstructure data, the beads are undoubtedly red precious corals, identical with modern corallium rubrum from the Mediterranean also confirmed by C- and O-isotopic analyses. The studies provide general criteria for the  determination of corallium rubrum, confirming the macroscopically determined identification of other coral artefacts associated with  the Hanseatic League, and thus prove their iconographic importance as well as the trade contacts with the Mediterranean region. However, the extent to which the characteristics of the coral beads indicate accidental or intentional individual or collective societal or  social circumstances is left to further study.