Material characterization of stone surfaces in the inner chambers of the Khufu (Cheops) Pyramid: towards informed conservation strategies

This study presents a systematic material characterization of the Queen’s and King’s Chambers stone surfaces of the Khufu Pyramid, conducted within the framework of the ScanPyramids mission. The two chambers show distinct interactions with their environment due to their differing lithologies. In the Queen’s Chamber, halite was identified as the main phase responsible for efflorescence on the massive limestone blocks. In the King’s Chamber, kaolinization of granite minerals appears to drive salt efflorescence formation in the upper blocks. Importantly, this research reports the first in situ application of X-ray fluorescence imaging for the characterization of Aswan granite. By mapping elemental distributions and correlating them with mineralogical phases, a completely non-destructive analysis of the granite surfaces was possible. In addition, a chemometric approach is proposed as an alternative to imaging for mineral-phase differentiation based on spot measurements. The study demonstrates how in situ portable non-destructive (contact-free) methods, combined with targeted micro-sampling, provide critical insights into deterioration mechanisms and support preventive conservation strategies for one of the world’s most iconic monuments.