Ancient Egyptian Granite Graffiti of Bigeh Island, Philae Archaeological Site (Aswan, Egypt): An Archaeometric and Decay Assessment for Their Conservation

This study investigates the deterioration of granite graffiti at the Philae Archaeological Site on Bigeh Island (Aswan, Egypt), attributed to Khaemwaset (1281–1225 BCE, 19th Dynasty). These graffiti, despite being carved into durable Aswan granite, are experiencing progressive degradation due to environmental and hydrological factors. This research aims to analyze the mineralogical and chemical transformations affecting the graffiti to provide a comparative assessment of submerged and unsubmerged granite surfaces. A multi-analytical approach was employed, combining petrographical examination, X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) to identify compositional changes and deterioration patterns. The results indicate mineralogical transformations in submerged and periodically exposed surfaces. The granite primarily consists of quartz, feldspar, and biotite, with notable alterations including kaolinization and illitization and dissolution of feldspar minerals and biotite oxidation. These processes are directly linked to prolonged exposure to fluctuating water levels and recurrent wet–dry cycles, which accelerate granular disintegration, exfoliation, and surface loss. Additionally, salt crystallization, particularly halite, contributes to granite weathering, while sulfate interactions promote chemical weathering. In addition, biofilm colonization, facilitated by high moisture retention, further exacerbates surface deterioration by producing organic acids that weaken the mineral matrix. Finally, the results confirm the need for conservation interventions to mitigate ongoing damage.