Mechanisms leading to the preservation of 5000-year-old textiles revealed by X-ray microtomography A multidisciplinary team has revealed FIGURE 1 the mechanism behind the exceptional preservation of textile remains from the Ancient East – the oldest archaeological textiles ever studied by advanced analytical methods. High-resolution and high-spatial- dynamic imaging of textile fibres in different photon energy domains allowed reconstructing a physico-chemical scenario explaining the preservation of their morphology at the nanometric scale. X-ray microtomography (µ-CT) data collected at the ANATOMIX beamline has been instrumental in determining the key steps of silicification, by identifying the spatial SEMIQUANTITATIVE SYNCHROTRON X-RAY distribution of the organic and mineral MICROTOMOGRAPHY phases present in these highly heterogeneous To appreciate this mechanism, archaeological cellulosic fibres, specimens. whose morphology was exceptionally well preserved close to copper-based objects in three sites from the Ancient East, were imaged by µ-CT at the ANATOMIX beamline with a spatial resolution EXCEPTIONAL PRESERVATION OF TEXTILE of less than 1 µm [2]. Phase identification was facilitated by the REMAINS use of a semiquantitative protocol to calibrate the intensities of the 3D reconstructed volumes [3, 4]. The protocol is based In Archaeology, fragments of ancient textiles can be particularlyon the estimation of the local attenuation coefficient μ (X) in valuable: in certain context, they provide us with the only each voxel X = (x,y,z) of the reconstructed volumes, accordingE accessible knowledge on entire textile productions for clothingto Lambert-Beer’s law, I = I exp (-∫ μ (X)dX), where the energy or ritual uses, but also for many technical functions such as the 0 E of the incident photons is noted E, the local attenuation being transport of materials, packaging or the production of objects.linearly correlated to the grey value in X of the reconstructed Unfortunately, organic textiles generally degrade very quicklyvolume. Numerical fitting of the µ-CT attenuation histograms in most environments. However, as early as the 19th century, was then used to identify the nature of the organic and mineral archaeologists excavating major sites in the Middle East notedphases and their distribution in the cellulosic fibres. In this way, the presence of identifiable textile traces, petrified on the surfaceit was possible to observe the presence of the siliceous phases of objects, often metallic (FIG. 1). This phenomenon, designatedin the cell walls of the most mineralized fibres and not only on later as “mineralization” by archaeologists, was observed even intheir surface (FIG. 2). contexts particularly unfavourable to the preservation of organic matter. Although they have been the subject of microscopic observations since the early 1960s [1], the complexity of these systems combining altered organic remains and mineral phases, as well as instrumental limitations, have long been obstacles to deciphering the “mineralisation” mechanism. 46