Off the shelf tool sheds light on precious artefacts
By Ben Coxworth
August 12, 2010
It’s rather ironic that in order to fully appreciate the value of an archeological artifact, part of that object must first be destroyed. That’s the way it has worked, at least, since the only way of determining the chemical composition of such items has been by breaking down a physical sample from them. As more and more institutions have decided to disallow sampling of their artifacts, however, it has become increasingly important to develop non-destructive methods of analysis. Recently, an archeologist from Tel Aviv University's Department of Archaeology and Ancient Near Eastern Civilizations developed just such a method – Professor Yuval Goren has adapted an off-the-shelf portable x-ray fluorescence (XRF) spectrometer to reveal the soil and clay composition of objects, simply by touching their surface.
Over many years of breaking down samples of various artifacts, archeologists such as Prof. Goren have built up a database of what combinations of minerals were used in items from what parts of the world. Now, data obtained through Goren’s XRF device can be cross-referenced with that database, to determine the geographical origins of a given item.
The spectrometer can be used on-site or in a lab, and can determine the composition of tablets, coins, plasters and glass.
In a recent study, Goren and his colleagues analyzed a late Bronze Age clay tablet, the style of which suggested it was an Arman letter – one of the many letters written from officials throughout the Middle East to the Pharaohs in Egypt around 3,500 years ago. By using the XRF device, the Tel Aviv University team was able to determine that the clay was typical of that found in the Terra Rossa soils of the Central Hill Country around Jerusalem. This data confirmed the suspected origin of the letter, and even suggested a possible sender.
"We believe this is a local product written by Jerusalem scribes, made of locally available soil. Found close to an acropolis, it is also likely that the letter fragment does in fact come from a king of Jerusalem," the researchers reported, adding that it may well be an archival copy of a letter from King Abdi-Heba, a Jesubite king in Jerusalem, to the Pharaoh in nearby Egypt.