Egyptian Blue: variability in production technology, material provenance and deterioration Eva Luna Ravan(1,2), Francesco Paolo Romano(2), Ariadne Kostomitsopoulou Marketou(3), Fani Pinakidou(4), Kalliopi Tsampa(5), Andreas Germanos Karydas(5), Hariclia Brecoulaki(6), and Claudia Caliri(2) (1) Sapienza University of Rome, Piazzale A.Moro 5, 00185 Rome, (Italy) (2) CNR-ISPC, Via Biblioteca 4, 95124, Catania, Italy (3) MF Norwegian School of Theology, Religion and Society, Oslo, Norway (4) School of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece (5) Institute of Nuclear and Particle Physics, NCSR “Demokritos”, Athens, Greece (6) Institute of Historical Research, National Hellenic Research Foundation, Athens, Greece Egyptian Blue (EB), one of the most commonly used pigment in antiquity, served as the primary blue pigment in artists' palettes until the 4th century CE [1] and in rare cases beyond. Its distinctive color derives from the orientation of copper (II) in the copper calcium tetrasilicate crystals (CaCuSi4O10, its naturally occurring but rare counterpart is the mineral cuprorivaite) [2]. Nonetheless, EB is a multicomponent material, the variability in its color, that can range from dark blue to almost white, can be attributed to differences in grain size, proportions of various mineral phases in the final product and manufacturing technology [3]. In our study we adopted a non-destructive multi-modal methodology, incorporating mobile analytical X-ray techniques, to analyze EB samples sourced from a variety of well-documented archaeological sites. The investigation encompassed wall painting fragments from late Classical and early Hellenistic Macedonian tombs. We have combined high-resolution 2D micro-XRF imaging (MXRF), 3D Confocal XRF mapping (CXRF) and 1D X-Ray Powder Diffraction (XRPD) available in the MOLAB platform of E-RIHS (ISPC-CNR, Catania, Italy). The non-destructive nature of this approach allowed for a thorough examination of the samples, yielding comprehensive analytical data. The findings offer deep insight into the choice of source materials, as evidenced by the XRF elemental analysis, and elucidate the crystalline environment of Cu-based pigments through XRPD. The use of micro-XRF imaging and 3D confocal XRF applied to the wall paintings fragments provides useful insights on the original painting techniques. The results of our research enable a better understanding of material provenance, technological changes, and the identification of ongoing deterioration mechanisms. [1] P. García-Fernandez, M. Moreno, J.A. Aramburu, J. Chem. Educ. 2016, 93, 111-117. [2] V. Daniels, R. Stacey, A. Middleton, Studies in Conservation 2004, 49:4, 217-230. [3] A. Kostomitsopoulou, F. Giannici, F. Caruso, Anal. Chem. 2021, 93, 11557-11567.