X-ray micro-CT helps archaeologists to write the biography of ancient ornaments

X-ray Micro-Computed Tomography (micro-CT) is an excellent technique to inspect small delicate beads. It reveals their composition and inner structure without damaging them. In particular the geometry of the narrow bead shafts becomes clear on micro-CT scans. Archaeologists can then draw conclusions about the way the beads were made, worn and, in some occasions, re-worked. The origin of the materials selected to make the beads, their production centre and trading routes can even be traced by combining micro-CT scans to other information, such as results of XRF analyses. Signs of post-burial deterioration become obvious. Forgery is easily detected. micro-CT scans also constitute a form of virtual preservation of the ornaments. Once stored in open source repository, they can be further exploited by various stakeholders (musea, archaeologists, the creative industry). The potential of micro-CT is illustrated for two collections of ancient Dutch ornaments: the Neolithic amber beads recovered from several graves and Early Iron Age frothy glass beads from Zutphen.
The role of amber beads in the materiality of burial practices in three different periods of the Dutch Neolithic has been investigated by combining microscopy and micro-CT. The scans allowed to evaluate the quality of manufacture and repair of the beads and detect signs of wear, re-shaping and post burial degradation. About 60 glass beads were recovered from an Early Iron Age urn-field near Zutphen (NL). Glass is rare in this period in the Netherlands and has been investigated, first, to determine from what primary glass production centre this glass originated, and by what route it could have reached the Netherlands, and second, to determine the nature and origin of the frothy structure of the beads. With its many glass bubbles, copper fillings and mineral inclusions, the glass of the Zutphen beads does not resemble glass from Mediterranean
production sites.