Assessing the copper-based metal diversity in the late 19th century in the Congo Basin using pXRF analysis

At the end of the 19th century, copper and brass were used in a large part of the Congo Basin to make ornaments and prestige objects. The main region of copper production in Central Africa exploited before the 20th century were the Copperbelt (S-E DRC) and the Niari Basin (South Rep. of Congo). However, while these areas would have provided a significant part of the copper consumed at the time, it is not excluded that other deposits supplied the Congo Basin. Furthermore, in the last decades of the 19th century, imported brass seems to have overshadowed local production of unalloyed copper. While the onset of colonial occupation seems to have played a role in this mass import, the chronology of these changes and the role of other brass suppliers, such as the Swahili trade in the east of the region, is still unclear. In addition to literature review and archival works, this talk will investigate whether portable X-ray fluorescence (pXRF) analysis can help to investigate the origin of the metal and pattern of trade and consumption in the Congo Basin at the end of the 19th century. It will be based on the analyses of a hundred copper-based objects originating from the region along the Congo River and some of its tributaries and curated at the Royal Museum for Central Africa. Key questions are, among others, whether other copper deposits than the Niari Basin and Copperbelt supplied the Congo Basin and to what extent imported brass overshadowed local copper production.info:eu-repo/semantics/nonPublishe

Non-destructive wood identification using X-ray µCT scanning: which resolution do we need?

Abstract Background Taxonomic identification of wood specimens provides vital information for a wide variety of academic (e.g. paleoecology, cultural heritage studies) and commercial (e.g. wood trade) purposes. It is generally accomplished through the observation of key anatomical features. Classic methodologies mostly require destructive sub-sampling, which is not always acceptable. X-ray computed micro-tomography (µCT) is a promising non-destructive alternative since it allows a detailed non-invasive visualization of the internal wood structure. There is, however, no standardized approach that determines the required resolution for proper wood identification using X-ray µCT. Here we compared X-ray µCT scans of 17 African wood species at four resolutions (1 µm, 3 µm, 8 µm and 15 µm). The species were selected from the Xylarium of the Royal Museum for Central Africa, Belgium, and represent a wide variety of wood-anatomical features. Results For each resolution, we determined which standardized anatomical features can be distinguished or measured, using the anatomical descriptions and microscopic photographs on the Inside Wood Online Database as a reference. We show that small-scale features (e.g. pits and fibres) can be best distinguished at high resolution (especially 1 µm voxel size). In contrast, large-scale features (e.g. vessel porosity or arrangement) can be best observed at low resolution due to a larger field of view. Intermediate resolutions are optimal (especially 3 µm voxel size), allowing recognition of most small- and large-scale features. While the potential for wood identification is thus highest at 3 µm, the scans at 1 µm and 8 µm were successful in more than half of the studied cases, and even the 15 µm resolution showed a high potential for 40% of the samples. Conclusions The results show the potential of X-ray µCT for non-destructive wood identification. Each of the four studied resolutions proved to contain information on the anatomical features and has the potential to lead to an identification. The dataset of 17 scanned species is made available online and serves as the first step towards a reference database of scanned wood species, facilitating and encouraging more systematic use of X-ray µCT for the identification of wood species