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Javagold – Scientific analyses of gold objects

Since the 1st millennium BC, goldsmith's work has played a special role throughout Southeast Asia.

On the various islands of Indonesia, gold jewellery was an expression of a special status in the social system.

On Java, gold jewellery was an indispensable part of Hindu-Buddhist court culture, although there are only small gold deposits on the island itself. During the classical period, 7th-16th century AD, ring jewellery was worn by both men and women. They were often worn in pairs on both hands, but other ways of wearing them, for example as pendants around the neck, are also documented.

Photos 1 und 2: Enlargement of a braided gold chain and granulation work on a chain. Photo: N. Lockhoff, CEZA.

Iconographically, the jewellery is clearly Hindu-Buddhist in character, but references to ancient traditions are also recognisable. In addition to ring jewellery, various forms of ear jewellery, headdresses, necklaces and belts as well as parts of ceremonial weapons, statues, votive plates and coins were also made of gold. This variety of forms reflects changes in society, religion and the economy and the associated different uses of “gold”. In the Early Classical period, gold objects were still part of the customary offerings, but this changed over time. Ritual objects are deposited in temples, rings and coins are traded as “valuables”. A selection of masterpieces of jewellery, insignia and art and cultural objects were presented in an exhibition at the Reiss-Engelhorn-Museen in 2019 and 2020. The CEZA has accompanied the research and analysis of the unique collection for many years with scientific investigations. Unfortunately, there are only a few archaeologically excavated and well-documented gold objects from the classical period, so the study of old collections in general is of great importance. In total, over 1400 gold and (silver) objects have already been scrutinised using scientific methods. The results of the research co-operation were also presented in the exhibition.

Due to the high intrinsic value, the analysis of gold objects should be as non-destructive or minimally invasive as possible. For this reason, non-destructive methods such as digital microscopy and X-ray fluorescence analysis were mainly used on metal, gemstones and glass. Minimally invasive laser ablation with mass spectrometry (LA-ICP-MS) was carried out on a smaller selection of objects. Other methods such as X-ray diffraction, scanning electron microscopy and metallography were used for specific questions.

While the Indonesian coin gold is predominantly heavily alloyed gold with high proportions of silver and copper, the statues analysed tend to have a significantly higher fineness of approx. 90 % Au. In the jewellery, the variation in alloy composition is significantly greater and in some cases trace element patterns can be observed that match those of workshop finds from Kota Cina (Sumatra).

Photo. 3: Cell for laser ablation. Here, samples or smaller objects can be sampled directly with a laser. The ablated material is then introduced into an ICP-MS analyser with a helium gas stream. Photo: C. Breckle, rem.

In the case of objects relevant to heritage history, the question of how to determine their age often takes centre stage. Metal artefacts are generally not directly scientifically datable. The gold objects in the collection had oxidised iron deposits in places, which also contained small amounts of carbon and could be dated using the 14C method. This is only an indirect dating method, which ideally reflects the age of the deposit. The possibility of direct dating of gold objects is also being researched as part of the co-operation. This new approach is based on the ability of gold to store the noble gas helium, which is produced during the radioactive decay of uranium, thorium and platinum. When it melts, the helium escapes from the gold and the “radioactive clock” is set to “zero”, so to speak. This should theoretically make it possible to directly date the last melting.