Sunday, September 23, 2012

Tomographic Reconstruction of the Selby Hoard

Tomography Analyzes Roman Coin Hoards
By Richard Giedroyc

X-ray computed tomography is now being used to examine damaged or corroded coin hoards in a major scientific breakthrough recently announced through the University of Southampton in collaboration with the British Museum. Tomography involves imaging by sections or sectioning using waves.

Until now, the primary use of tomography has been in archaeology, astrophysics, biology, geophysics, materials science, oceanography, quantum information and in radiology. Numismatics, as a science related to archaeology, can now be added to the list using what is generally called tomographic reconstruction.

The Selby Hoard of ancient Roman coins discovered with a metal detector near Selby, East Riding, York, in England was the subject of the first tomographic reconstruction of a coin hoard. In this case the coins were lumped together in the ground when first encountered. Eleanor Ghey is the archaeologist who has been studying this hoard. 


It has been determined that the coins date between the time of Roman Emperors Vespasian and Hadrian, and include coins of Marcus Aurelius and Trajan as well. The Southampton’s µ-VIS Centre for Computed Tomography used an x-ray technique that takes thousands of two-dimensional scans from which a compilation resulted in the 3D animation images of the coin hoard. 


The high energy/high resolution ability of the Southampton facility allowed the coins to be examined in detail without having been cleaned or examined physically. Visualization capabilities were used to identify the rulers depicted on the coins through the iconography and inscriptions on the coins.

Dr. Graeme Earl is an archaeologist with the University of Southampton. He was recently quoted as saying, “Excavating and cleaning just a single coin can take hours or even days, but this technology gives us the opportunity to examine and identify them quickly and without the need for conservation treatment at this stage. It also has potential for examining many other archaeological objects.”


 The availability of tomographic reconstruction to examine concreted coin hoards is an important development which promises to be of significant benefit to archaeologists, hoard discoverers and collectors alike. In these days of bitter political stalemate and oppositional confrontation regarding the disposition and repatriation of excavated artifacts, a development such as this that everyone can welcome is a rarity. 

In addition to the benefits to archaeology discussed above, tomographic reconstruction promises to make it feasible to rapidly determine whether conservation treatment to remove the coins in a hoard from their concretion mass is warranted, from a balanced perspective taking into account all legitimate interests including those of the discoverer and landowner. 

Since this beneficial assessment process requires a major scientific laboratory, it will of course not be available to "nighthawkers" and others who illicitly excavate coins. That would in this observer's view become one more step in the direction of discouraging illicit excavation of coins through economic pressure, by far the most effective approach (as I have often pointed out, in the end everyone obeys the laws of economics).

Cheers to the University of Southampton, the British Museum, Eleanor Ghey and all others involved in the extension of this technique to study of the Selby Hoard. Their pioneering work promises to have far-reaching impact in putting the study and eventual disposition of concreted artifacts on a more scientifically sound and rational footing.



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