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Ancient silver-based alloys objects are of a great interest because they were world-wide used to produce high value works of art and precious items as jewels and ornaments with a relevant artistic, religious or historical value. Silver-based alloys were also largely used everyday as monetary currency and form of saving playing a relevant role for the development and growth of the economy. By means of the combined use of complementary surface analytical techniques such as scanning electron microscopy coupled with energy dispersive spectrometry (SEM + EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and optical microscopy (OM) we have investigated the micro- and nano-chemical nature of the products of corrosion naturally formed on archaeological silver-based Roman objects characterised by different burial conditions. The results allow the identification of different corrosion products formed during the long interaction between the elements constituting the alloy, i.e. Ag and Cu, and degradation agents present in the surrounding environment. The results of the integrated analytical methodologies highlight the role of chlorine, that is always present in the patina as chloroargyrite (AgCl, also known as cerargyrite or horn silver) and also in some cases of bromine which forms bromargyrite (AgBr) or bromian-chloroargyrite [Ag(Br,Cl)] as dominant corrosion products. The unusual presence of Br in the silver patina reflects the peculiar environmental chemistry suffered by the buried object likely due to the presence of degrading organic matter under aerobic conditions. Furthermore, the results reveal that chlorine often preferentially corrodes the numerous local copper enrichments randomly dispersed in the silver host matrix inducing the formation of harmful copper-chlorine compounds including Cu 2 Cl(OH) 3 (atacamite and its polymorphs) and likely CuCl (nantokite) generally related to the copper cyclic corrosion called by conservators “bronze disease”. Finally, different corrosion patterns have been observed with the outermost layers often enriched by soil elements as S, Ca, Al, Si and Fe thus confirming the strong interaction of the alloys elements with the burial soil components. [ABSTRACT FROM AUTHOR]

Different pyrometallurgical materials such as slags, refractory materials and thermally treated lead ores likely related to smelting and extractive processes and chronologically related to Punic and Roman periods (IV–III BC) have been found at Bocche di Sciria and Conca e Mosu in the Montevecchio mine basin (south western Sardinia, Italy), where archaeological findings and classical authors locate extractive metallurgy activities since pre-Roman times. By means of the combined use of X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectrometry (EDS), selected-area X-ray photoelectron spectroscopy (XPS) and optical microscopy (OM), micro-chemical and micro-structural investigations have been carried out in order to identify the nature of the pyrometallurgical materials, to decipher the processes carried out there and their technological steps and to determine the technological level of competence reached by the ancient metallurgists. The results confirm that the findings can be associated with smelting and extractive processes carried out close to the metal ore deposits first for the argentiferous lead production and, then, for the silver recovery via a cupellation process. Finally, the results disclose the high level of technological competence of the ancient metallurgists able to carry out complex high-temperature processes to treat the argentiferous lead ores and to recover low amounts of silver via high-temperature lead-selective oxidation. [ABSTRACT FROM AUTHOR]

Six cases of ancient silver embrittlement by corrosion are discussed with respect to evidence for stress corrosion cracking. Both intergranular and transgranular cracking can occur, depending on whether there is retained cold-work in the silver. The severity of cracking is influenced by a combination of factors, including the amount of cold-work in the silver and the burial environment. The burial environment is important for two reasons. Firstly, the soil weight can induce high stresses, particularly in hollow, thin-walled, and incompletely filled-in artefacts. Secondly, grave burials can result in more aggressive soil environments owing to high salinity from body decomposition. [ABSTRACT FROM AUTHOR]

This article discusses six cases of ancient silver embrittlement. The diagnostic techniques and results are surveyed, followed by the most likely explanations of embrittlement. There are two basic types of embrittlement: corrosion-induced, and microstructurally induced, which can act synergistically. Corrosion-induced embrittlement takes several forms, including what appears to be intergranular and transgranular stress corrosion cracking. The main intrinsic factor facilitating corrosion-induced embrittlement is retained cold-work in the silver. Microstructural embrittlement is characterized by intergranular fracture, most probably due to low-temperature segregation of lead to the grain boundaries. Knowledge of the details of embrittlement can be essential for optimizing the restoration and conservation of damaged artifacts. [ABSTRACT FROM AUTHOR]

This article examines a collection of Hellenistic silver objects acquired by the Metropolitan Museum of Art in New York City in 1981 and 1982. The collection includes a deep bowl with rounded bottom, a circular medallion consisting of a thin metal sheet, a pitcher with ovoid body and a small cylindrical alter on a quadrangular base. An analysis of the objects' conditions, inscriptions, monograms, weight indications, and manufacture is included. A detailed description of the objects is also given.