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As one of the most desired and expensive artists' materials throughout history, there has long been interest in studying natural lapis lazuli. The traditional method of extracting the blue component, lazurite, from lapis lazuli, as outlined in Cennini's Il Libro dell'Arte, involves a lengthy purification process: (1) finely grind the rock; (2) mix with pine rosin, gum mastic, and beeswax; (3) massage in water to collect the lazurite. Repeating the process produces several grades of the pigment, typically referred to as ultramarine blue. Here, we investigate the sulfur environment within the aluminosilicate framework of lazurite during its extraction from lapis lazuli. The sulfur XANES fingerprint from samples taken at the different stages in Cennini's extraction method were examined. All spectra contain a strong absorption peak at 2483 eV, attributable to sulfate present in the lazurite structure. However, intensity variations appear in the broad envelope of peaks between 2470 and 2475 eV and the pre-peak at 2469.1 eV, indicating a variation in the content of trisulfur (S3-) radicals. By studying the effect of each step of Cennini's process, this study elucidates the changes occurring during the extraction and the variability within different grades of the precious coloring material. The increasing application of XANES to the study of artist's materials and works of art motivated extending the research to assess the possibility of X-ray induced damage. Direct comparison of micro-focused and unfocused beam experiments suggests an increase of the S3- radicals with prolonged exposure. Analysis indicates that induced damage follows first-order kinetics, providing a first assessment on the acceptable amount of radiation exposure to define the optimal acquisition parameters to allow safe analyses of lapis lazuli and ultramarine pigments. [ABSTRACT FROM AUTHOR]

Pliny the Elder's 'Natural History' is often cited in studies of ancient natron glass production. Pliny describes the production of glass using sand from the Belus River in Israel and the Volturno River in Italy. He also mentions that glass was similarly made in France and Spain. However, no direct archaeological evidence has ever been found to support glass production in these regions. In this study we investigate the possible existence of a Roman primary glass industry in the western Mediterranean, based on the occurrence of suitable sand raw materials. 178 beach sands from Spain, France and Italy are evaluated for their suitability for glass production by calculating the composition of hypothetical glasses made from these sands and comparing them to Roman natron glass. The results show that good glassmaking sands are far from common. Only six limited areas could be defined where suitable sand raw materials would have been available to the Roman glassmaker. The rest of the sands are unsuitable for glass production in their present form. The suitability of the suggested sands was checked by performing a series of melting experiments, which provide further insights in the way Roman glass makers would have had to prepare their raw materials and the used batch recipes. [ABSTRACT FROM AUTHOR]