Analysis of Gilding Technology in Prehistoric Jewelry from the Silk Road

Analysis of Gilding Technology in Prehistoric Jewelry from the Silk Road

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Analysis of Gilding Technology in Prehistoric
Jewelry from the Silk Road These objects were found in cemeteries along
what is known as the prehistoric Silk Road. These are spiral ornaments about a centimeter
in diameter that were worn as pendants that are made up of a copper core that was covered
over with a very thin silver/gold foil, 50 to 100 micrometers in thickness. There are
indications they were enriched, gilded on the surface to make them look more like pure
gold. The earliest example of this kind of this
process in this part of the world, they date from 1800 to 1750 BC, nearly 4,000 years old.
We saw indications of enrichment of gold on the surface of the foils covering these artifacts.
So, what we needed to do was look at interface between the area of gold enrichment at the
surface and the more silver-rich interior of this foil.
I came to EMSL because there was interest, from past experiments, in working with archeological
materials, including ancient metalwork. What we needed was a technique that would
give us a very – very, very good high resolution of the interface between these zones in the
foil, and so we utilized the NanoSIMS instrument to do that. The question was whether there was a very
abrupt division between the gold and silver-rich zones or whether it was more diffused, which
was an interesting question in terms of the ancient technology that is very important
for the archeology of the region. We were really interested to see if the NanoSIMS
would be able to give us a very good view of the interface between the gold and silver-rich
zones in these foils. We found out that the boundary between the
gold enrichment on the surface of the jewelry and the silver-rich interior on the foil covering
it was in fact a rather diffuse boundary, indicating that the process that was probably
used was one that’s known as depletion gilding, or the removal of silver from the surface
to make this silver/gold alloy to look more like solid gold. And this has very important
implications for the history of technology in this very early period in Asia. How the
utilization of these techniques may be a part of a broader history that led up to purification
of gold in later periods. Another very important implication is that
there may have been transfer of technology along what became the Silk Road later, much
earlier in prehistory. It’s very important to me to have facilities
like EMSL for research in archeology, because all the time we’re developing new questions
based on previous research, and very often the available technology to address those
questions in our own labs is not sufficient to effectively do that. So having access to
facilities like EMSL is absolutely crucial to be able to address these questions and
to improve our knowledge of ancient human interactions. Visit our website at www.emsl.pnnl.gov. While
you’re there, find out how you can become an EMSL user and access EMSL’s resources at
no cost for published research.

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