E. Gliozzo

Pigments and Plasters Discovered in the House of Diana (Cosa, Grosseto, Italy): An Integrated Study Between Art History, Archaeology and Scientific Analyses*

The pigments and the plasters of the Roman frescoes discovered at the House of Diana (Cosa, Grosseto, Italy) were analysed using non-destructive and destructive mineralogical and chemical techniques. The characterization of both pigments and plasters was performed through optical microscopy, scanning electron microscopy and electron microprobe analysis. The pigments were identified by Raman spectroscopy and submitted to stable isotope analysis. The results were integrated with the archaeological data in order to determine and reconstruct the provenance, trade patterns and the employment of the raw materials used for the elaboration of the frescoes.

Mineralogical, petrographic and geochemical characterisation of white and coloured Iberian marbles in the context of the provenancing of some artefacts from Thamusida (Kenitra, Morocco)

A multi-analytical study has been carried out on a collection of white and coloured Iberian marbles. A total of 135 marble specimens were collected in Spain and Portugal from the Betic chain (Alhaurin de la Torre, Mijas, Macael), Ossa Morena (Alconera, Almaden de la Plata and Viana do Alentejo), and the Estremoz Anticline (Bencatel, Borba and Estremoz) areas. X-ray diffractometry and carbon and oxygen stable isotope analysis were carried out on these samples; 38 samples were also investigated by optical and scanning electron microscopy. The results provide a set of diagnostic parameters that allow discriminating the sampled marble quarries. The carbonate minerals composition is distinctive for the Mijas and Alhaurin de la Torre marbles; the isotopic analysis allows discriminating also between these two dolomitic marble quarries. The Ossa Morena and Estremoz Anticline marbles share a similar stable isotope composition; the accessory mineral content, the maximum grain size (MGS) and the fabric are particularly useful in the distinction between them. In the framework of archaeometric provenance studies on Thamusida (Kenitra, Morocco) Roman marble artefacts, a specific comparison between this new Iberian database and archaeological findings has been carried out. The hypothesis of commercial exchanges between the Iberian regions and Roman Morocco is supported by the results of the provenance study, which suggested the Almaden de la Plata and Mijas quarries as possible sources of raw materials for the production of archaeological artefacts.

Colourless glass from the Palatine and Esquiline hills in Rome (Italy). New data on antimony- and manganese-decoloured glass in the Roman period

A collection of 21 glass samples (18 colourless and 3 light aqua blue) found in recent excavations performed at the Palatine and Esquiline hills in Rome has been investigated by means of SEM-EDS, EMPA and LA-ICP-MS. The glass was recovered in the “Baths of Helagabalus” and the Horti Lamiani. The collection included cups and bowls widely attested in Rome and Ostia from the late second to the first half of the third century AD. The analyses assigned this collection to the RC/LAC-MnSb groups (Roman and Late Antique colourless glass with both antimony and manganese) which seemed closely related to the Levantine area.

Tuscan black glosses: A mineralogical characterization by high resolution techniques

Tuscan black glosses on ancient pottery have been characterized using high resolution techniques. Ancient (4 th -1 st century B.C.) pottery from southern and northern Tuscany is coated with black glosses which show different visual appearance. Misfired red-black, matt, shining, metallic, and bluish black glosses have been studied with X-ray diffraction, scanning and transmission electron microscopes to establish their mineralogical, textural and chemical characteristics. The glosses are chemically homogeneous and they are all comprised of a Si-Al rich, amorphous matrix where nanometer-sized crystals of different nature are embedded. Crystals occur both as euhedral grains and as grains with a high aspect ratio. The misfired gloss contains hematite as the only mineral phase, both in the red and black portion of the coating. The matt black gloss contains mainly homogeneous hercynite crystals. In a small portion of the gloss, few magnetite crystals have been detected. However, no gradual variations either along or perpendicular to the gloss layer have been observed. Magnetite is the only mineral phase occurring in the shining metallic black gloss. The bluish-black gloss shows spinel grains with variable characteristics. Most grains are comprised of homogeneous hercynite with magnetite in solid solution. Other crystals are zoned: the core has hercynitic composition with relatively high content in magnetite, ulvospinel, and spinel s.s. in solid solution; Al and Mg increases towards the rim. These results clearly indicate that microanalytical techniques provide accurate mineralogical and microtextural characterizations at the nanometer scale. It has been shown that visually different glosses have different mineralogy which are mainly caused by different oxygen fugacities (f O2 ) during firing.

Neutron diffraction of Cu–Zn–Sn ternary alloys: non-invasive assessment of the compositions of historical bronze/brass copper ternary alloys

Neutron diffraction can be used as a tool for the characterization of metal materials in a totally non-invasive mode. In binary alloys with two elements in solid solution, crystallographic structure analysis provides information on the overall element compositions of the metal, based on the linear relationship between elemental fractions and lattice parameters known as Vegards rule. However, for ternary solid-solution alloys the derivation of the overall metal composition is not straightforward because the problem is mathematically underdetermined. A number of artificially produced samples in the ternary system Cu–Zn–Sn, widely used in antiquity for gunmetal, were investigated by time-of-flight neutron diffraction, inductively coupled plasma mass spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy and electron microprobe analysis. The multi-analysis approach allows definition of the limits and capabilities of neutron diffraction for obtaining the overall composition of a small sample set of ternary alloys, and thus moves the methodical approach a step forward even though it is applicable to the present sample set only. A relation showing an increasing Cu and Sn fraction counterbalanced by decreasing Zn content is presented, which allows the determination of the δ-phase composition from a lattice parameter measurement. Furthermore, the observed Zn loss up to 1.8 wt% for each melting step is of significance for the reconstruction of ancient technologies.

Marbles and carbonate rocks from central Morocco: a petrographic, mineralogical and geochemical study

Petrographic, mineralogical, and stable isotopes (δ13C, δ18O values) compositions were used to characterise marbles and sedimentary carbonate rocks from central Morocco, which are considered to be a likely source of ornamental and building material from Roman time to the present day. This new data set was used in the frame of an archaeometric provenance study on Roman artefacts from the town of Thamusida (Kenitra, north Morocco), to assess the potential employment of these rocks for the manufacture of the archaeological materials. A representative set of samples from marbles and other carbonate rocks (limestone, dolostone) were collected in several quarries and outcrops in the Moroccan Meseta, in a region extending from the Meknes–Khenifra alignment to the Atlantic Ocean. All the samples were studied using a petrographic, mineralogical and geochemical methods. The petrographic and minerological investigations (optical microscopy, electron microscopy, X-ray diffraction) allowed to group the carbonate rocks in limestones, foliated limestone, diagenetic breccias and dolostone. The limestones could be further grouped as mudstones, wackestones–packstones, crinoid grainstones, oolitic grainstone and floatstones. Textural differences allowed to define marbles varieties. The stable carbon and oxygen isotope composition proved to be quite useful in the discrimination of marble sources, with apparently less discriminatory potential for carbonate rocks.

Application of the Rietveld method for the investigation of mortars: a case study on the archaeological site of Thamusida (Morocco)

This study presents a multi-technique approach to the investigations of mortars, involving the application of the Rietveld method. The quantitative mineralogical analysis of samples was aimed at (1) verifying its significance in relation to results obtained through other techniques and (2) evaluating its potential in mortars characterisation. Six type of mortars used in the Roman settlement of Thamusida (50 km north of Rabat, Morocco) were investigated through X-ray powder-diffraction and Rietveld refinement, optical microscopy, image analysis, scanning electron microscopy, electron microprobe analysis, X-ray fluorescence (XRF) and combined differential thermal, and thermogravimetric analysis (DT–TGA). All the adopted techniques yielded unique results and complementary data; however, the Rietveld method can actually substitute thermal analysis accurately. CaO oxide contents obtained by DT/TGA and Rietveld are in good agreement, but both were only partly comparable to XRF results. In our case, XRF and Rietveld results diverge when binders contain more than 67 wt.% CaO. The discrepancies can mainly be ascribed to the presence of amorphous material and to the obtainable accuracy by QPA-Rietveld method; conversely, the nonstoichiometry of phases does not affect our results, because phases with variable compositions are present in small amounts. Results further showed that the adopted methods were suitable for mortar characterisation. All studied mortars (1) have weak hydraulic properties; (2) employed binders characterised by highly variable CaO contents and by significant amounts of SiO2; (3) used coarse to fine quartz–carbonate-rich sands as the aggregate; and (4) selectively mixed 2 or 3 parts of aggregate with 1 part of binder, depending on the destination of the mortar.

Glass ingots, raw glass chunks, glass wastes and vessels from fifth century AD Palatine Hill (Rome, Italy)

The research focused on a collection of 20 glass fragments, including raw glass chunks and ingots, wastes and vessels found at the Palatine Hill in Rome and dated to the first half of the fifth century AD. The analyses performed by scanning electron microscopy (SEM)-energy-dispersive spectrometry (EDS), electron microprobe (EMPA), inductively coupled plasma mass spectrometry (ICP-MS), laser ablation-ICP-MS (LA-ICP-MS) and X-ray diffraction (XRD) showed that all samples are constituted by natron-based soda–lime–silica glass. De/colouring agents were lead stannates (yellow brownish), copper and lead antimonates (green), different Fe2+/Fe3+ ratios (green, light green and yellow-green), Fe2+ (prevailing over Fe3+; aqua blue), cobalt (blue), metallic copper (reddish) and manganese (colourless). As for provenance, two samples were of Levantine provenance, nine samples were likely of Egyptian origin (HIMT glass) and, similarly, seven samples (or maybe nine, adding ingots nos. 1–2) were likely of North African provenance (HIMT/RNCBGY 1 glass).

New geochemical and isotopic insights into the Late Antique Apulian glass and the HIMT1 and HIMT2 glass productions—the glass vessels from San Giusto (Foggia, Italy) and the diagrams for provenance studies

The research focused on a collection of 37 Late Antique glass fragments, found at the archaeological site of San Giusto (southern Italy). The analyses performed by SEM-EDS, EMPA and LA-ICP-MS showed that all samples are constituted by natron-based soda-lime silica glass and allowed clarifying the distinction between Egyptian HIMT1 and HIMT2 productions. The comparison with the composition of the available glass reference groups was verified through three ternary diagrams (provided here for the first time). The results grouped San Giusto samples into HIMT1 (7 samples), HIMT2 (8 samples) and Levantine (13, plus maybe other 3 samples) productions. A convincing provenance assignment was not feasible for six samples only. The isotopic analyses (87Sr/86Sr and 143Nd/144Nd), performed on a selected set of ten samples, provided further information both in terms of glass technology and provenance, as well as in terms of reference groups characterisation. Particularly, the results demonstrated that nine out of a total of ten samples were made using a limestone-bearing sand enriched with variable amount of marine shells and provided further evidence for the distinction of the HIMT1 and HIMT2 groups; the latter overlapping the Levantine field in the 87Sr/86Sr versus εNd binary diagram. From a technological point of view, the importance of separating the likely ‘fresh’ materials from those intentionally recycled or coloured was put into clear evidence, especially in relation to provenance assignments. Lastly, an interesting technological feature has been observed in sample no. 9, where the composition of the main body of the vessel turned out to be different from that of the handle. This result provided clear evidence of the fact that different glass batches could have been used for the different parts of a single vessel body.

SR-Based Molecular Speciation of Archaeomaterials

Examples are presented of the use of SR modalities for the molecular characterisation of archaeomaterials. They focus on the utilisation of the most basic of synchrotron radiation properties, high brilliance and energy range that can be selected. Two techniques have been employed, X-ray diffraction and X-ray absorption spectroscopy, to characterise the mineral composition of painting pigments and pottery glazes.