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The ware called Taches Noires was developed in Albisola (Liguria, NW Italy) during the 18th century. In just a few years, it spread all over the Mediterranean (Italy, France, Spain, Tunisia, and Greece) and also in the New World (Canada, the Caribbean Islands, and Mexico). The success of the Taches Noires ware was so massive that it was soon copied by Spanish and French workshops. A collection of Catalan imitations and Ligurian imports found in Barcelona were analysed and compared to previously existing data from Barcelona productions, as well as reference samples from Albisola. The study proved the presence of both local imitations and original Albisola imports. The analysis showed a homogeneous product of high technical quality for the Albisola pottery. On the contrary, the local imitations presented a greater diversification in the choice and manipulation of the raw materials, probably related to the existence of different workshops engaged in the manufacturing of these products. Nevertheless, for one of the local groups, ceramists adopted a glaze recipe similar to the one used in Albisola, clearly indicating a direct transfer of knowledge, and possibly of potters, from Albisola to Barcelona.

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Hexagonal neo-formed crystallites have been observed in thin section of different medieval and post-medieval lead-glazed ceramics. Although they are clearly visible in thin section using plane polarized light, their plate shape makes them barely seen on the polished cross sections. Basal sections have never been found on the polished sections and only few transversal very thin sections could be seen. In this case, the morphology resembles acicular and it is not possible to analyze them properly by SEM-EDX because the crystals are very thin and the glaze surrounding is analyzed as well. Micro-Raman microscopy was carried out directly on the polished thin sections. This technique allows specific areas as small as 1 μm in diameter to be analyzed and it is able to characterize inclusions that are not found on the glaze surface. However, the wavenumber features observed cannot be assigned to a specific compound. The thickness of the crystallites (a few hundred nanometers) seems to be responsible for the low sensitivity of the Raman instrumentation. 15 × 15 μm 2 micro-X-ray diffraction patterns using synchrotron radiation (SR-μXRD) in transmission geometry were obtained from the crystals using the same thin section preparation. SR-μXRD was able to localize the crystallites and avoid the overlapping signals corresponding to other mineral phases. In this way, the hexagonal crystallites present in the glaze have been unambiguously identified as hematite crystallites. Finally, some replications were made under laboratory-controlled conditions to determine the firing conditions in the formation of those crystallites. The presence of hematite coexisting with melanotekite indicates a firing temperature <925°C, while the presence of only hematite suggests a firing temperature >925°C ARTICLE HISTORY

Galena, also known as PbS, was widely used in the production of lead glazes from the beginning of the 18 th century to the second half of the 20 th century. Although the SiO 2 -PbO system has been studied for years, the PbS- Accepted ArticleThis article is protected by copyright. All rights reserved.melts at a temperature higher than the PbO-SiO 2 system, but far lower than those expected for the PbO-PbSO 4 -PbS system. A historical misfired lead glaze produced with galena is also studied. The presence of galena, lanarkite and mattheddleite Pb 10 (SiO 4 ) 3.5 (SO 4 ) 2 Cl 2, is determined and discussed in terms of the composition of the galena mineral used and the firing conditions in light of the high temperature transformations previously obtained.

In the Neolithic Gavà mines, variscite and turquoise were exploited for ornaments manufacturing, although some prospective pits and tunnels were dug on other similar greenish minerals such as smectite or kandite. A 3D study of the distribution of mineral phases allows us to determine the parameters involved in variscite colours. Methods are comprised of quantitative colourimetry, thin section petrography, SEM-BSE-EDS, EMPA, XRD, Raman spectroscopy, and 57Fe Mössbauer spectrometry. Mapping of the mines indicates that colour is not directly dependent on depth. Although variscite from Gavà is poor in Cr3+ and V+3 compared with gemmy variscite from other localities, the deep green samples content has the highest values of Cr3+. In the case of cryptocrystalline mixtures with jarosite, phosphosiderite, or goethite, variscite tends to acquire a greenish brown to olivaceous hue. If white minerals such as quartz, kandite, crandallite, or alunite are involved in the mixtures, variscite and turquoise colours become paler.

During the last thirty years, microstructural and technological studies on ceramic glazes have been essentially carried out through the use of Scanning Electron Microscopy (SEM) combined with energy dispersive X-ray analysis (EDX). On the contrary, optical microscopy (OM) has been considered of limited use in solving the very complex and fine-scale microstructures associated with ceramic glazes. As the crystallites formed inside glazes are sub- and micrometric, a common misconception is that it is not possible to study them by OM. This is probably one of the reasons why there are no available articles and textbooks and even no visual resources for describing and characterizing the micro-crystallites formed in glaze matrices. A thin section petrography (TSP) for ceramic glaze microstructures does not exist yet, neither as a field of study nor conceptually. In the present contribution, we intend to show new developments in the field of ceramic glaze petrography, highlighting the potential of OM in the microstructural studies of ceramic glazes using petrographic thin sections. The outcomes not only stress the pivotal role of thin section petrography for the study of glaze microstructures but also show that this step should not be bypassed to achieve reliable readings of the glaze microstructures and sound interpretations of the technological procedures. We suggest the adoption by the scientific community of an alternative vision on glaze microstructures to turn thin section petrography for glaze microstructures into a new specialized petrographic discipline. Such an approach, if intensively developed, has the potential to reduce the time and costs of scientific investigations in this specific domain. In fact, it can provide key reference data for the identification of the crystallites in ceramic glazes, avoiding the repetition of exhaustive protocols of expensive integrated analyses.

Photomicrographs of thin sections provide a swift and efficient means of sharing information for consultation, education, documentation and publication within the Geosciences and related areas. In general terms, the main way to capture digital microscopic images involves the use of a mounted camera unit on a high‐end costly benchtop microscope. However, freehand methods to capture microscope‐scale images using a smartphone, as well as smartphone adapters that can be attached to a microscope have emerged during recent years. This paper presents the design features of a costless system able to obtain photomicrographs without requiring a conventional microscope. The imaging device is comprised of a mini‐objective lens attached to a smartphone and a structure that allows it to focus as well as to rotate the stage and to insert/remove a polarized sheet. The quality and magnification of the images attainable from the new design is comparable to the images normally obtained by a conventional petrographic microscope using a ×4 objective and a ×10 ocular (total magnification ×40).