A Sardinian early 1st millennium BC bronze axe from Motya

An Iron Age bronze axe was found in Motya (Sicily, Italy) in a prehistoric layer dating from the 10th century BC underneath the 4th century BC patrician residency known as “Casa dei mosaici”. The axe belongs to the double-looped socketed type well known in central Mediterranean in the time span 1200-900 BC, and it is comparable with some coeval Sardinian specimens. The bronze has been characterised using the backscattering electron signal of a SEM (Scanning Electron Microscope) and EDX (Energy Dispersive X-ray Spectroscopy). The resulting composition of the metal alloy is Cu-Sn-As with an addition of Pb in some specific spots

Micro-Raman spectroscopy and complementary techniques applied for the study of copper and iron wastes from Motya (Italy)

This work is the first archaeometric investigation on copper and iron wastes from the Phoenician site of Motya (Sicily, Italy), dating back to the 8th to the 4th century BC. The samples were analyzed through micro-Raman Spectroscopy (μ-RS), Optical Microscopy (OM), Scanning Electron Microscope-Energy-Dispersive X-ray Spectroscopy (SEM-EDS), High-Resolution Field Emission Scanning Electron Microscopy (HR-FESEM), and Electron Micro-Probe Analysis (EMPA). Micro-Raman techinique permitted to identify both primary phases, for example, calchopyrite, and secondary products such as cuprite and copper thrihydroxychlorides in the Cu-slags and goethite in the Fe-slags. SEM and HR-FESEM imaging showed the occurrence of inhomogeneous microstructures in the Cu- and Fe-slags due to elements segregation, solidification, and corrosion. EMPA data revealed that the archaeometallurgical wastes from Motya can be differentiated on the basis of their chemical compositions. These preliminary results showed different typologies of by-products, such as base metals speiss, copper slags from smelting sulfide ore with matte, and iron smelting and smithing slags, suggesting different stages of copper and iron productions

Microstructure and chemical composition of Iron Age archaeological objects from the Phoenician-Punic site of Motya (Sicily, Italy)

The aim of this work was to characterize chemical composition of the alloys and corrosion microstructures of Phoenician bronze weapons from the archaeological site of Motya (western Sicily, Italy). For this purpose, some bronze artifacts were selected and studied by the combined use of different analytical techniques, such as scanning electron microscope (SEM-EDS) and electron microprobe analysis (EMPA). Moreover, X-ray maps on cross section of the artifacts were also performed to obtain information about elemental distribution in the different layers. Quantitative analysis from rim to core sections has been acquired using EMPA in order to estimate different composition of major and minor elements of the original alloy. The results revealed that binary (Cu-Sn) and ternary alloys (Cu-Sn-Pb) with some impurities of As compose the weapons. A common feature of quite all samples is represented by dissolution of copper in outermost layers (i.e., decuprification process) as well as widespread presence of chlorine as the main corroding agent. However, different microstructures of the alloys were observed, i.e., an axe shows a matrix of low tin bronze with large and insoluble Pb globules, which undergo oxidation processes, forming oxidized lead compounds on the patina; other artifacts display complex stratified corrosion layers with a periodicity, recognized as the Liesegang effect (Scott, 2006), which is related to the occurrence of chloride compounds. The study of the microstructures and the stratigraphy of these metal artifacts allow having new insights about corrosion process and the nature of the alloys as well as on metallurgical background of Phoenicians. Scott D. A. 2006. Periodic Corrosion Phenomena in Bronze Antiquities. Studies in Conservation, 30(2), 49.https://doi.org/10.2307/150608

Archaeometric investigation of bronze arrowheads from the Siege of Motya (Sicily)

Nine Phoenician bronze arrowheads were characterized by means of scanning electron microscope (SEM-EDS), electron microprobe analysis (EMPA) and X-ray diffraction (XRD). These archaeological arrowheads were recovered from the archaeological site of Motya (western Sicily, Italy) and attributed to the siege by Dionisio I, tyrant of Syracuse, in 397 B. C. In particular, scanning electron microscope (SEM-EDS) and X-ray maps was performed on cross section to characterize qualitative chemical composition of the artifacts, distribution of the alloy elements in the different layers and corrosion microstructures. Quantitative analysis from rim to core sections has been carried out using electron microprobe analysis (EMPA) to determine the composition of major and minor elements of the alloy. X-ray diffraction (XRD) was used to define the mineralogical composition of the corrosion products. This systematic study allowed the conic arrowhead to be identified as binary alloy (Cu-Sn) with complex banding corrosion layers, known as the Liesegang rings. Indeed, the bilobed and trilobed arrowheads were made by ternary alloys (Cu-Sn-Pb), showing a Cu-Sn matrix with Pb globules, which are oxidized to form lead salts on the patina. The presence of copper trihydroxichlorides seems to be strongly correlated with the size of the Pb-globules. This is the first scientific attempt to characterize the bronze arrowheads found in Motya, by relating the microstructures and the alloy compositions with their typologies and probable geographic provenances. This research gives new insight on weaponry and poliorcetics of the Syracusan army

Conventional and advanced techniques for archaeological diagnostic of iron artefacts

In this paper, an overview of corrosion processes on iron-based artifacts from Motya (western Sicily, Italy) is proposed. A review of the research contributions is given concerning two main topics: (i) the study of the interaction between iron weapons and the lagoon-like environment of Motya by means of spectroscopic and microscopic analyses. The results are compared with those obtained from the study of armors found in the Punic Necropolis of Lilybaeum (4th century BC, Sicily), which permit to define different corrosion models; (ii) the characterization of corrosion of iron nail (IV century BC) through a multi-modal and multi-scale approach using a X-Ray tomographic technique to get a comprehensive understanding of the structure, morphology, stratification, chemical composition and corrosion mechanisms

Evaluation of stress corrosion and micro-segregation in copper-based artefacts through X-ray Microscopy

The role of alloying elements in production technology and corrosion process has been investigated in different type of archaeological copper-based artefacts from the Phoenician-Punic site of Motya (Sicily, Italy). For this purpose, a combination of multi-analytical techniques (Multiscale X-ray Microscopy, SEM, HR-FESEM- EDS and EMPA) has been carried out to investigate the inner bulk of the alloy, performing tomographic virtual slices of the objects, and exploring grain boundaries segregation at sub-microscale. All copper-based artefacts were exposed to bronze disease corrosion induced by the presence of the reactive cuprous chloride (CuCl) located at the interface between external corrosion layers and the surviving metal core. The results highlighted micro-segregation in a Cu-nail induced by As, which was forced outwards along inter-granular channels and combined with Fe atoms at Cu grain boundaries, leading to the formation of copper-iron arsenate, due to the high chemical affinity between these two elements. Binary and ternary alloys revealed marked Cu and Sn selective corrosion and thicker patina compared with Cu metal due to the presence of Sn in chlorine-rich environment. The dissolution factor of copper in these alloys showed a great variability. In addition, the occurrence of cracks inside the bronze needle acted as new corrosion interfaces and involved the formation of complex and periodic stratified corrosion layers, leading to a complete mineralized structure

A comprehensive strategy for exploring corrosion in iron-based artefacts through advanced Multiscale X-ray Microscopy

The best strategy to tackle complexity when analyzing corrosion in iron artefacts is to combine different analytical methods. Traditional techniques provide effective means to identify the chemistry and mineralogy of corrosion products. Nevertheless, a further step is necessary to upgrade the understanding of the corrosion evolution in three dimensions. In this regard, Multiscale X-ray Microscopy (XRM) enables multi-length scale visualization of the whole object and provides the spatial distribution of corrosion phases. Herein, we propose an integrated workflow to explore corrosion mechanisms in an iron-nail from Motya (Italy) through destructive and non-destructive techniques, which permit the extraction of the maximum information with the minimum sampling. The results reveal the internal structure of the artefact and the structural discontinuities which lead the corrosion, highlighting the compositional differences between the tip and the head of the iron nail

On-Tech: characterization of ancient mortars for the development of new sustainable materials

One of the main challenges in the field of conservation is the development of innovative restoration products respecting the environment and the operator who works on cultural heritage. In this scenario, mortars and building materials require special attention especially because of the CO2 production linked to the cement industry, which is the third anthropogenic source of this type of emissions. This project, therefore, aims to provide innovative mortars resistant and compatible with ancient materials, which minimize CO2 emissions and are environmentally friendly. The mortars were produced starting from the ancient Roman recipe used for the Traiano-Paolo Aqueduct (Rome, I-II century A.D.) which proved highly resistant and durable thanks to a perfect mix of raw materials, grain size and production technology. The first phase of the study concerns the characterization of the starting raw materials considered perfect in terms of compatibility with ancient materials. In detail, pozzolans from different quarries around Bracciano Lake (Rome) were sampled to assess their characteristics. The mineralogical-petrographic and chemical composition have been studied through a multi-analytical approach. The results showed several differences in matrix, leucite crystals (presence, size, type), amount of phenocrystals (clinopyroxenes and feldspar) and porosity. For the experimental step the vesicular pyroclastic materials, with abundant crystals of leucite, clinopyroxenes and high porosity were chosen as starting material for the new formulations which were then characterized through the use of optical microscopy (OM), X-ray diffraction (XRPD), Fourier infrared spectroscopy (FTIR) and scanning electron microscopy (SEM-EDS)

Micro‐Raman spectroscopy and complementary techniques for the study of iron weapons from Motya and Lilybaeum (Sicily, Italy). Corrosion patterns in lagoon‐like and calcarenitic hypogea environments

Micro-Raman spectroscopy (mu-RS) has been used to characterize mineralogical phases of corroded iron materials, buried in lagoon-like and calcarenitic hypogea environments. A set of samples from the Phoenician site of Motya (8(th)-6(th) centuries BC, Sicily) and from the Punic Necropolis of Lilybaeum (4(th) century BC, Sicily) were analyzed combining mu-RS with scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) and high-resolution field emission scanning electron microscopy (HR-FESEM). Micro-Raman results revealed the presence of magnetite, goethite, lepidocrocite, and hematite as the main corrosion products and soil minerals as quartz, calcite, barite, actinolite, microcline, zircon, and Ti-oxides. SEM and HR-FESEM allowed exploring micro- and sub-micrometer structures of iron oxy-hydroxides though sections from rim to core. The different corrosion models suggest polymorphic inter-conversions among iron oxy-hydroxides and dissolution-re-precipitation reactions. In addition, the occurrence of magnetite and metal core that survived in armors buried in the hypogea site of Lilybaeum indicates more stable environmental conditions than those of Motya