Inclusions and metal composition of ancient copper‐based artefacts: a diachronic view by micro‐EDXRF and SEM‐EDS

Abstract

A diachronic view of the metallurgy in the Portuguese territory during the first three millennia after its appearance in the Iberian Peninsula is presented based on the current state of the art. Results of micro‐energy dispersive X‐ray fluorescence (micro‐EDXRF) analyses made on metal artefacts to determine their composition and scanning electron microscopy with energy dispersive analysis (SEM‐EDS) analyses to study microstructural features as inclusions are shown to illustrate trends and specificities of each chronological period. Generally, in early periods, namely during the Copper Age and first stages of the Bronze Age, unalloyed copper and arsenical copper were at use, and only by the Late Bronze Age (LBA) did tin bronze substitute almost completely the previous role of copper. In the Early Iron Age, during the Orientalising period, a general decrease in the average tin content in bronzes seems to happen. Regarding the inclusions observed in the metal matrix, these seem to suffer a diversification with the appearance of tin bronzes. By the Copper Age, only CuO and CuAsO inclusions are observed, while by the LBA CuS inclusions become regular, besides others less frequent, as SnO, CuSFe and Pb globules. Overall, with the present analytical study, the complementary character of micro‐EDXRF and SEM‐EDS in the study of ancient metals is demonstrated, providing a first general overview of the ancient metallurgy at the Portuguese territory which is of key importance to specific investigations of the future. Copyright © 2011 John Wiley & Sons, Ltd.

New insights on Late Bronze Age Cu-metallurgy from Coles de Samuel hoard (Central Portugal): A combined multi-analytical approach

“…This kind of inclusions have already been reported in LBA bronzes from the Portuguese territory and can be likely considered as micro-inclusions from the original ore material used in the production of the artefacts (Figueiredo et al, 2011). Moreover, and although a relatively low tin amount (10 ± 1 wt%), the α + δ eutectoid phase has been observed as well (Fig.…”

“…Also in the case of socketed axes, the SEM-EDS characterisation allowed the identification of some of the most common inclusions observed in the LBA metals from the Portuguese territory (Figueiredo et al, 2011), namely Ag (Fig. 7), Pb and Cu-S, as well as the α + δ eutectoid richer in tin (Fig.…”

Study of corrosion in archaeological gilded irons by Raman imaging and a coupled scanning electron microscope–Raman system

“…Regarding elemental images, the scanning electron microscope (SEM) is extensively used for cultural heritage research purposes [22,23]. Its magnification feature and its ability to identify most of the elements helps researchers to thoroughly understand the composition of the alloys used for the specimen as well as to understand the presence of layers or heterogeneities.…”

Microstructural characterisation of a collection of Protohistoric bronzes

“…Different types of inclusions were identified, namely copper sulphides, tin oxide, and lead rich inclusions. Both copper sulphides and lead inclusions are commonly found in archaeological bronzes [1,2], and can be a result of copper ores impurities. Tin oxide, on the other hand, is not so common, and its presence can be understood as a result of preferential oxidation of tin regarding copper during a melting or alloying operation [3].…”