Researchers Unravel Secrets of a 6,000-Year-Old Amulet
A scientific analysis of mysterious amulets dated back to 3,000 BC has brought new information to light about ancient metallurgy techniques. One copper amulet is the earliest lost-wax cast object known in history.
According to Phys.org, a team of researchers has a new explanation about technologies used for copper amulet production in the third millennium BC. By using a novel UV-visible photoluminescence spectral imaging approach, they could detail the parameters of the production process - such as the purity of the copper and melting and solidification temperatures.
The collection of small amulets was discovered in 1985 at the archaeological site of Mehrgarh in today's Balochistan in western Pakistan. The researchers believe that the amulets may have been created for religious purposes. However, the copper artifact focused on in their study had not been fully examined in three decades. As physicist Mathieu Thoury of the synchrotron SOLEIL lab in France told International Business Times :
“Scientists had reached the limits of what they could learn from the amulet with traditional imaging techniques, and could not solve the paradoxes regarding how it had been manufactured. We have designed a full-field photoluminescence approach to look at the object's structure and composition in greater details. This has allowed us to infer what the amulet was made of when it was first created six millennia ago, based on what it is made of now.”
Comparison of high spatial dynamics-photoluminescence (PL) (top), and optical microscopy images (bottom). The area shown corresponds to part of one of the spokes of the amulet. The PL image reveals a eutectic rod-like structure that is undetectable in all of the other tested techniques. The image allowed the researchers to explain the process used to make the amulet. © T. Séverin-Fabiani, M. Thoury, L. Bertrand, B. Mille, IPANEMA, CNRS / MCC / UVSQ, Synchrotron SOLEIL, C2RMF
The new information came about through a collaboration between researchers from the CNRS, the French Ministry of Culture and Communication, and the SOLEIL synchrotron. They documented their work in an article published in the journal Nature Communications .
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The lost-wax method is used to duplicate metal sculptures cast from an original mould. The method is still in use today, but until now evidence of its usage during the Neolithic period was limited. However, the procedure hasn’t changed much since Neolithic times. This procedure is often believed to be the result of technological innovations in many other areas, like: dentistry, pottery making, and textiles.
The lost-wax technique was crucial in the history of metallurgy. With time, it became popular across the Middle East, Mesopotamia, and the Mediterranean region. People started to create not only amulets, but also small figurines and other items with this method.
A collection of small lost-wax cast ornamental objects found during excavations at the MR2 site at Mehrgarh. ( D. Bagault, B. Mille, C2RMF )
The researchers described the process of making the amulet: it began with creating a model formed in a low melting point material, such as beeswax, which was covered with clay. The model was heated to remove the wax and baked to create a mold, which was then filled with copper.
To confirm the usage of this method, the team of scientists used a photoluminescence technique that works by shining light on the objects they wanted to analyze. Through this process they observed that two copper oxides were present in the sample. The same physical and chemical patterns appeared to be present across the surface of the sample, suggesting that the amulet was cast as a single piece. The presence of copper oxides proves that it was made from a pure copper melt.
The archaeological site in Mehrgarh where the amulet was found. (C. Jarrige/Mission archéologique de l’Indus )
Amulets are some of the most fascinating and mysterious ancient artifacts. April Holloway reported on two other interesting Neolithic pendants on Ancient Origins in November 2013. She wrote:
“In 1914, a Swiss amateur archaeologist, Ernest Roulin, approached the Museum of Science and Art in Ireland with an incredibly rare discovery – two ancient amulets made from fragments of human cranium. The amulets were dated to around 3,500 BC, during the Neolithic period, and have led to some fascinating conclusions regarding the practices and beliefs of our ancient ancestors. The amulets are oval in shape and perforated towards one end, possibly for threading so that the item could be worn around the neck. The edges are well finished and rounded, which also suggests that they were worn or displayed as pendants.”