Chemistry

The analytical techniques used in the field of cultural heritage are as far as possible non or almost non-invasive. Among them those based on proton beams show for gold fingerprinting, a good compromise between detection limits and destructiveness. The main characteristics of PIXE, PIGE, PIXE-XRF and proton activation analysis (PAA) are given for the study of gold alloys. Their main advantages and disadvantages are cited and their use in the field of archaeological sciences is illustrated by two historical examples. One example concerns the identification of the origin of the gold used in the decoration of the coffins from a Xiongnu necropolis (3rd c. BC to 2nd c. AD) found in present Mongolia. The other example establishes whether the coins attributed to the first king of Portugal, Alfonso I, were struck in the 12th century or in modern time.

Tracing gold back to its source by means of the elemental composition of objects contributes to the knowledge of the trade routes used in the past. The analysis of a large number of ancient gold objects showed that in most cases only a few elements are useful to characterize the metal. Quantitative analysis of these elements was performed on a set of gold samples with different techniques: inductively coupled plasma mass spectrometry in liquid mode and with laser ablation, 12 MeV proton activation analysis, fast neutron activation analysis, particle induced X-ray emission (PIXE) and PIXE induced X-ray fluorescence. The aim of this paper is to present a discussion on the possibilities and limitations of these techniques to characterize gold.

Problems concerning the determination of technology and provenance of archaeological metals are presented using several historical examples and considering the heterogeneity of the alloys. PIXE and XRF are compared to other techniques (PIGE, nuclear activation, LA-ICP-MS); their limitations and complementary aspects in obtaining historical information are discussed.

nuFrom the study of coins and casted simple objects to intricate jewellery comprising many diverse parts joined together, analytical queries on ancient goldwork concern the description of the manufacturing techniques, the identification of the authenticity and the localisation of the exploited sources of gold. Through the examination of the objects by x-ray radiography and the non-destructive elemental analysis of the gold alloys – by XRF, SEM-EDX, PIXE and SR-XRF, x-ray based techniques have always played an important role in the study of cultural heritage and, in particular, of goldwork.

The aim of this article is to give a short overview of the use of the most established scientific-based techniques in the study of goldwork, with special outlining on the limitations, advantages and applications of x-ray based techniques. Two applications illustrate both the potential of examination techniques to identify the authenticity of gold jewellery and the importance of combining examination techniques and elemental analysis to describe the fabrication stages of goldwork. At last, a third example shows the significant socio-economical assumptions developed by determining the characteristic trace elements of gold when coinages are considered.

This chapter focuses on the study of the characterization and provenance of coins and other metal work using XRF, PIXE and activation analysis. The aim of this work is to give a general description on the usage of radiation techniques for determining the provenance of metals and understanding the manufacture technology of metallic objects. The main properties and differences for the most useful techniques are given in the chapter. Some complement radiation techniques are also considered. The chapter also lists several examples of metalwork, most of them on coinage, and important non-ferrous metals and alloys used in the past. These cover a large but far from complete number of fields of research. It is demonstrated that provenance may sometimes be determined by using trace elements patterns. For each main metal, after some geological, smelting and purification considerations, application of the radiation techniques to the manufacture technology and the provenance of the ores were considered to answer a number of particular historical questions.

The analysis of the gold coinages struck in the Iberian Peninsula from the Visigoths to the recovery of the territory from the Muslim by the Christian Kings, gives an economical survey of the region during about seven centuries. Either supplied with local or with external gold ores, the Iberian Peninsula follows the evolution from the apogee to the decline of several cultures. During that time, periods of gold abundance, such as under the Arabian dynasties which had access to the West African gold, follow periods of scarcity during the wars. A set of coins issued in the Iberian Peninsula during the concerned seven centuries was analysed by proton activation analysis (AAP) and by inductively coupled plasma mass spectrometry (ICP-MS) with a laser ablation.

Little is known about goldsmithing during the period of the Great Kushans. In order to undertake a first approach to the technological choices and the gold alloys used in the fabrication of the different parts of Kushan objects, five gold jewellery items from the collections of the National Museum of Antiquities of Tajikistan containing wires and granulation were transported from Dushanbe to Paris to be studied within the European research project “AUTHENTICO” with non-destructive scientific-based techniques at the C2RMF. All the items were found in archaeological excavations carried out in the 1970s in several regions of Tajikistan and were examined by optical microscopy, scanning microscopy, and X-ray radiography. The compositions of the alloys were determined by ion beam analysis (PIXE) at the AGLAE accelerator.

Non-destructive elemental analysis and examination provide paramount information for authentication of gold jewellery items kept in museum collections with no reference documents. A small group of Etruscan objects from the Campana’s collection, assembled in the 19th century, were studied by optical microscopy, SEM, X-radiography, and PIXE in order to establish criteria for the discrimination of genuine objects, pastiches and modern restorations. We could show that: the morphology of wires and granules from ornamental patterns added to enhance the objects separate in some cases modern from ancient parts; the composition of the alloys showed in other cases the different steps of construction of an object.

The casket of Queen Maria Pia of Savoy, belonging to the collection of the Palácio Nacional da Ajuda, contains a set of thirty-three pieces of gold jewellery in the archaeological style created by the Castellani workshop in Rome. This family of jewellers, fascinated by the ancient techniques of gold working, restored but also reproduced several antique pieces, giving rise to the emergence of the so-called ‘archaeological jewellery’, very popular in the 19th century, using characteristic techniques of antique jewellery such as granulation, filigree, micro-mosaic and engraving of stones in intaglio.
The main purpose of this paper is to present the results of the analyses of the base metals used in the manufacture of the jewellery and also to identify the production techniques, such as mounting, joining and decoration, used by the Castellani workshop in making the jewellery for the casket of Queen Maria Pia of Savoy. For this purpose, portable equipment of examination and analysis was brought to the museum. The results obtained in situ show the use of standard wires and granules, as well as of three different base alloys. One element of a hairpin pair which appears to have originated from a different production is discussed.

La détermination de l'origine et de la provenance de l'or utilisé dans la fabrication de bijoux et monnaies anciens se base sur l'analyse élémentaire d'éléments traces caractéristiques d'un gisement. Cet article aborde les derniers développements de méthodes d'analyse élémentaire, non destructives ou utilisant des micro-prélèvements, pour mesurer les éléments traces présents dans les alliages d'or, puis montre l'application de ces méthodes à l'étude de différents procédés métallurgiques de production du métal ainsi qu'à l'identification de la provenance de l'or utilisé dans la fabrication de bijoux mycéniens et de monnaies et bijoux islamiques.

A small gold figurine found at the site of El Angel, far from the coast threshold, is usually associated with the Tumaco La Tolita goldsmith traditions, in spite of a location outside the cultural area of this civilisation. The study of the figurine by non-destructive scientific methods, evidencing the different steps of production, such as joining and decoration, shows that the object was remounted. However, the majority of its main parts are genuine.
The composition of the alloys and especially the presence of Fe, Pd and Pt are typical of the gold used in the production of La Tolita Tumaco objects. The analytical results attest that the figurine from El Angel, in Sierra, could have been one of the exceptional objects exported far away from its geo-cultural area."