From remote sensing to digital reconstruction: Islamic gold mining in the eastern desert De la prospection spatiale à la reconstitution numérique : orpaillage médiéval dans le Désert Oriental En Fr

Résumé En

The Mission Archéologique Française du Désert Oriental (MAFDO) founded by H. Cuvigny and then directed by B. Redon, T. Faucher and now by M. Crépy, has been exploring Ptolemaic and Roman forts, roads, quarries, and mines in the Eastern Desert of Egypt since 1994 and has been excavating 19 archaeological sites. In 2013, the mission started a systematic survey in the vicinity of the excavations. Since 2020, the mission is based at Ghozza, a Hellenistic gold-mining village and a Roman fort, both located in the northern bank of the eponym wadi. Thanks to preliminary digital surveys of the area using satellite images, the mission discovered a later, dense network of medieval camps composed of huts and gold-processing installations from the Abbasid and/or Tulunid periods. To proceed to an exhaustive survey, despite the vastness of the desert areas to be checked, we used remote sensing and satellite images to identify the main areas of interest and structures requiring field inspection. The data was gathered into a GIS, which made it possible to visualize and monitor the progress of digital survey, and then to guide on-field investigations and archaeological operations. In 2023, in the center of one of the spotted areas of interest, the survey revealed the presence of an extremely well-preserved washing table that we fully documented thanks to photogrammetry. To better understand this occupation, as the vicinity of the washing table had been heavily looted by present-day gold miners, the mission decided to proceed in 2024 to archaeological study of another sector corresponding to a small camp, located 250 m away, in which surface pottery was similar to the one found near the washing table. On site, a photogrammetric survey was systematically carried out, prior to any intervention, to obtain high-resolution zenithal images to complement the satellite imagery, and to produce precise three-dimensional representations. This digitization helped to establish a typo morphology of the structures, classifying them into two main categories: huts and storage tanks. Medieval gold-miners used the latter to store powder made from gold-bearing quartz processed using rotative grinding stones. After that, they had to wash the gold bearing quartz powder with water to separate the quartz from the heavier gold particles. But this step of the chaîne opératoire was poorly documented by archaeology as very few gold washeries from medieval times have been recovered in Egypt and none of them had been completely digitized. The study of the camp uncovered two more washing installations, deeply intricated in the local topography, whose blurred shapes and boundaries can hardly be rendered using traditional representation techniques. The digitization and three-dimensional representation of these structures and their immediate surroundings before and after the cleaning, using photogrammetry and 3D rendering, are therefore ideal.Ultimately, to better understand, represent and disseminate the use of these structures, a three-dimensional restitution has been undertaken. It completes a digital continuum from satellite imagery to the production of media dedicated to the dissemination of information to the scientific community, via the stages of mapping and analysis on the field and in the laboratory. The aim of this paper is therefore to show how the combined use of several digital data acquisition and processing techniques in the framework of archaeological work helped to answer some of the questions raised by the medieval gold rush in the Eastern Desert, and facilitated a work made difficult by the spatial extent of the archaeological remains and their tenuousness.