This work follows the recent discovery of a zinc-bearing Egyptian Blue (EB) pigment widely used for the production of the early medieval mural paintings cycle in Santa Maria foris portas church at Castelseprio (Lombardy Region, Italy).The inclusion of zinc in the synthesis of EB has been studied for the first time trying to evaluate whether its addition could be casual or deliberate. Historical reconstructions of the pigment have been carried out with a special focus on the use of zinc besides copper, using different production methods. The influence of zinc on the pigment's NIR photoluminescence and VIS-NIR reflectance has been characterized using FORS spectroscopy, X-Ray diffraction, optical microscopy, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy. A comparison of production methods including salt-flux, solid state and Zn-rich syntheses showed that solid-state synthesis results in particularly efficient NIR photoluminescence and VIS-NIR reflectance. Modern replicas were compared to an ancient sample in order to understand the zinc environment inside the structure of the Zn-enriched EB. Zn was found to be concentrated in a glass-based matrix surrounding cuprorivaite crystals, the main mineral associated with the EB pigment, and not included in a Zn-doped cuprorivaite with formula CaCu 1-x Zn x Si 4 O 10. The Zn-rich synthesis opens up the possibility of producing EB from brass and demonstrates that EB used in Castelseprio's mural paintings could have been produced in this way. The relationship between the microstructure and the NIR photoluminescence of cuprorivaite-like pigments is of interest also for applications in modern and future technologies.

Reports is aimed at archaeologists and scientists engaged with the application of scientific techniques and methodologies to all areas of archaeology. The journal focuses on the results of the application of scientific methods to archaeological problems and debates. It will provide a forum for reviews and scientific debate of issues in scientific archaeology and their impact in the wider subject. Journal of Archaeological Science: Reports will publish papers of excellent archaeological science, with regional or wider interest. This will include case studies, reviews and short papers where an established scientific technique sheds light on archaeological questions and debates.

The ancient pigment Egyptian blue has long been studied for its historical significance; however, recent work has shown that its unique visible induced luminescent property can be used both to identify the pigment and to inspire new materials with this characteristic. In this study, a multi-modal characterization approach is used to explore variations in ancient production of Egyptian blue from shabti statuettes found in the village of Deir el-Medina in Egypt (Luxor, West Bank) dating back to the New Kingdom (18th-20th Dynasties; about 1550–1077 BCE). Using quantitative SEM-EDS analysis, we identify two possible production groups of the Egyptian blue and demonstrate the presence of multiple phases within samples using cluster analysis and ternary diagram representations. Using both macro-scale non-invasive (X-rays fluorescence and multi-spectral imaging) and micro-sampling (SEM-EDS and Raman confocal microspectroscopy) techniques, we correlate photoluminescence and chemical composition of the ancient samples. We introduce Raman spectroscopic imaging as a means to capture simultaneously visible-induced luminesce and crystal structure and utilize it to identify two classes of luminescing and non-luminescing silicate phases in the pigment that may be connected to production technologies. The results presented here provide a new framework through which Egyptian blue can be studied and inform the design of new materials based on its luminescent property.

The ancient Egyptian blue pigment was developed over 5000 years ago and was used extensively for around four millennia until its use mysteriously declined dramatically during the Early Middle Ages. It recently attracted a lot of attention along with some related materials, leading to a fast-growing number of applications in fields, such as sensors, solar concentrators, energy-saving, and medicine. The new surge in interest began in 1996 with the discovery of their intense NIR photoluminescence that surprisingly can be triggered even by visible light. In 2013, the possibility of exfoliating them and producing NIR luminescent nanosheets was established, expanding the family of 2D nanomaterials. More recently, the discovery of their high antibacterial effects and biocompatibility, and very promising optical, electric and magnetic properties, has further boosted their applications. The characteristics of Egyptian blue are due to its main component: the very stable crystalline compound CaCuSi4O10. This tetragonal sheet silicate is the synthetic analogous of the rare cuprorivaite mineral. In Part A of this review, we summarize the historical uses and main properties (i.e., composition, structure, color, stability, luminescence, and biological activity) of cuprorivaite and related 2D silicates, i.e., BaCuSi4O10 (the main constituent of the ancient pigment Chinese Blue), BaCuSi2O6 (the main constituent of the ancient pigment Chinese Purple), SrCuSi4O10 (synthetic analogous of wesselsite) and BaFeSi4O10 (synthetic analogous of gillespite). The Part B of the review will focus on the modern rediscovery of these materials, their modern synthesis and exfoliation, and the innovative applications based on their properties.

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