X-Ray Fluorescence Spectrometry can help researchers to determine where a letter was written.  An analysis of the recently discovered cuneiform tablet from Jerusalem reveals that it was written on local clays.  This supports the theory that Jerusalem in the 14th century BC was ruled by kings with an educated class of scribes. From the American Friends of Tel Aviv University:

But Prof. Goren’s process, based on x-ray fluorescence (XRF) spectrometry, can go much further. Over the years, he has collected extensive data through physical “destructive” sampling of artefacts. By comparing this data to readouts produced by the XRF device, he’s built a table of results so that he can now scan a tablet — touching the surface of it gently with the machine — and immediately assess its clay type and the geographical origin of its minerals.
The tool, he says, can also be applied to coins, ancient plasters, and glass, and can be used on site or in a lab. He plans to make this information widely available to other archaeological researchers.
[…]
Its style suggests that it is a rough and contemporary tablet of the Amarna letters — letters written from officials throughout the Middle East to the Pharaohs in Egypt around 3,500 years ago, pre-biblical times. Using his device, Prof. Goren was able to determine that the letter is made from raw material typical to the Terra Rossa soils of the Central Hill Country around Jerusalem. This determination helped to confirm both the origin of the letter and possibly its 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.

The full release is here.

HT: Joe Lauer