Corroborating the autoptic identification of archeological glyptics in museum collections: the contribution of portable Raman spectroscopy

A collection of Hellenistic–Roman glyptics, kept at the Regional Archaeological Museum “Paolo Orsi” (Syracuse, Italy), was investigated in situ with portable Raman spectroscopy with the aim of assessing the viability of this approach, not only for the immediate identification of the gemstones but also for a more in-depth successive data treatment. At the same time, a corroboration of the autoptic identification of the materials, both archeological and belonging to historical collections, was looked for in order to verify and potentially correct what reported in the museum catalogue. Actually, most of the identifications could be confirmed, the glyptics being mainly made of chalcedony. Other materials found were garnet, glass, and amber. The larger group of chalcedony Raman spectra was subjected to principal components analysis treatment that, after appropriate pretreatment, resulted successful in separating spectra with higher or lower contribution of the band due to the presence of moganite and Si OH bonds. The garnet spectra were instead subjected to quantitative study to identify the main end member. Both the quick identifications and the more detailed studies on chalcedonies and garnets were achieved thanks to the nondestructive and noninvasive investigation, directly in situ, with no sample preparation and minimal interference with the museum's activities

The source of blue colour of archaeological glass and glazes: the Raman spectroscopy/SEMEDS answers

The founding of lapis lazuli to give blue colour to glass and glazes is more and more coming out from the most recent studies of pottery and glassware of different epochs and provenances. The recent discovery in the south of Italy (Frederick II, Melfi castle) of enamelled glass pieces including blue enamels questioned the real nature of the blue colour raw materials because the castle is built over and not far from outcrops of two volcanic rocks – haüynophire and phonolite – that contain haüyne, mineral belonging to sodalite group as lazurite, that can be blue or become blue after heating. Raman microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy were tested in order to identify the rock used as raw material and to understand if the chromophore-bearing mineral in the artefacts could be other than lazurite. To do this, the two volcanic rocks, lapis lazuli and archaeological glass with blue enamels, were studied. In particular, temperature-dependent Raman measurements and Raman mappings both on single lazurite and haüyne crystals and on the rocks and the enamels were carried out also in order to investigate the colouration mechanism of haüyne. The results obtained allowed to make hypotheses about the transformations occurring in haüyne with heating and about the procedures of distinguishing the raw materials

Mobile Raman spectroscopy analysis of ancient enamelled glass masterpieces

Richly decorated enamelled glass objects and fragments of different provenance and epoch have been analysed using mobile and fixed Raman instruments: some fragments of the outstanding Begram treasure (Musee des arts asiatiques - Guimet, Paris) dated to the 1st century AD, mosque lamps and bottles of Syrian/Egyptian provenance dated to the 13th/14th century (collections of Musee du Louvre and of Musee des arts decoratifs, Paris). The techniques are compared using the data obtained from the study of a group of similar objects and fragments discovered in Melfi Castle in the South of Italy in an archaeological context dated to the last quarter of the 13th century. The glass body was difficult to analyse requiring the use of high-energy high-power laser beams and/or sampling that allowed determining the soda-lime type precisely. In contrast, a variety of colouring agents was identified: lapis lazuli and/or cobalt for blue, antimonate pyrochlore solid solution for yellow, with the addition of cobalt/lapis lazuli for green, hematite for red and calcium phosphate/cassiterite/calcium antimonate for white. Where present, gilding was found applied on a rough and matt red enamel base probably in order to guarantee the physical adherence of the gold leaves. The comparison between the above mentioned groups of objects and between them and data existing in the literature about Roman enamelled glass allowed us to follow the evolution of the technology of this class of precious artefacts and to discuss the potential of the mobile Raman analysis

Diversified production of red figured pottery in Apulia (Southern Italy) in the late period

Late Apulian red figured pottery [1] from Egnatia (Fasano, Brindisi, ITALY) was studied in order to widen the view on this ceramic class in Southern Italy. Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) provided the samples elemental composition that allowed to make provenance hypotheses. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometry (EDS), supplied information about the minero-petrographic features of the objectsto better understand their production technology. The set of results highlighted the contemporary presence in the Apulian land in the late 4th century b.C. of both local and imported finds and showed the existence of two different kinds of local production, the "classic" Attic and a peculiar one, characterized by the application of an engobe layer before the black gloss. Our previous studies resulted in the discovery that an engobe layer, with similar chemical and minero-petrographic characteristics, was found in finds from another site in central Apulia (Monte Sannace). So the discovery of red engobe on fragments from Egnatia, proves that its use was not an isolated occurrence, but was quite common in the production of red figured in Apulia during the Late period, appearing as a peculiar technological mark of Apulian potters

Multi-spectroscopic approach to explore the technological features of medieval gilded and enamelled glasses from Melfi (PZ)

Gilded and enamelled glasses of Islamic style, coming from a 13th century landfill in Melfi castle, a Swabian emperor Frederick II fortress, were subjected to a multi-techniques approach in order to explore the complex and very fascinating ancient production technology of gilding and enamelling on glass. Non-destructive μ-Raman spectroscopy was employed on the most important and well-preserved objects, optical (OM) and electron (SEM) microscopies were used to investigate the sections stratigraphy of tiny fragments sampled from the borders of the already damaged objects. In order to provide the chemical analyses of the bodies and the enamels, energy dispersive X-rays spectroscopy (EDS) and X-rays photoelectron spectroscopy (XPS) were also employed. The body of the objects proved to be made of silica-soda-lime glass, while the enamels of lead-rich glass (“soft enamels”) and coloured by lapis lazuli and cobalt for blue, hematite and minium for red, lead-tin yellow for green and calcium phosphate for white. The gilding was found to be applied on a red enamel basis. The presence of carbon inside the gildings and the detection of two different gold signals by XPS suggested the hypothesis of the use of the so-called “liquid gold”. This study gave thus an important contribution to the understanding of the production of this class of rare and precious objects, also confirming that the materials and technological procedures are consistent with the Islamic tradition, probably due to the presence of Islamic artisans at the court of Frederick II

An analytical techniques pool to hit the target. A comprehensive examination on an Apulian red figured pottery collection

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A multi-analytical approach to amber characterisation

Increased need for non-destructive investigation methods in archaeology has become a major issue since sampling is in most cases restricted in view of the importance or uniqueness of the objects. For this reason, preliminary investigation using non-destructive techniques was performed on five samples of amber beads obtained from different excavation and archaeological sites. The use of FTIR and micro-Raman analysis revealed the presence of carboxyl, peroxide, hydroxyl, and complex ester functional groups as well as single and double bonds in the structure of the studied resin varieties. Further analysis of the amber samples from both archaeological and geological types by XPS, XRF, and SEM showed the presence of sulfur and a wide range of trace elements on the surface of the analysed samples. Our results proved that the combination of structural-molecular and surface elemental techniques for amber characterisation provides a very useful and simple methodology for the description of geological and archaeological amber samples from different regions of Europe