Old meets new
CLS used to examine museum coins

March 26, 2010

By Mark Ferguson

Researchers from the Museum of Antiquities are hoping an experiment at the Canadian Light Source synchrotron (CLS) could shine some light on the origin of some very old coins and, at the same time, revolutionize a technique for identifying archeological specimens without having to ruin them.

On most days, the biomedical beamline at the CLS is a busy spot for health research on living specimens, but the focal point for this experiment is a flat, metallic coin that could be over 2000 years old. Each of the 18 coins used in the experiment is either too dirty or too worn for experts to tell where, or when, they are from, said Tracene Harvey, director of the museum and archaeological scholar involved in the experiment. Some of the specimens are so decrepit they appear like they would crumble if touched.

“These coins are in various states of survival,” said Harvey. “Most of them are in pretty rough shape but coins are vital to the archeological record. If we can date them correctly, we can tell what the economic activity was like at the site the coins were from.

“Our goal for this experiment is to find a way to identify the coins quickly, efficiently and accurately. If we can refine the technique here (at the CLS), then the synchrotron could be a huge asset to archeologists, and a way to bridge the gap between sciences and humanities.”

The small sample of 18 coins represent a collection of approximately 350 that was given to the museum about 10 years ago by private donor, Robert McCorkell. The collection is worth tens of thousands of dollars and though Harvey suspects they are either Roman or Greek coins from the second, third or fourth century (based on thickness), they are so worn and unreadable that they cannot be precisely identified. And that is where the CLS comes in.

According to Tomasz Wysokinski, CLS scientist and adjunct professor of engineering, the biomedical beamline can penetrate the metal and reveal markings and characteristics left behind– almost like a shadow – making it easier to identify the coins.

“From my point of view, I would say we have a 50 to 60 per cent success ratio where we can actually see some relief on the images of the coin,”  said Wysokinski. “It’s a tricky business because you see both sides of the coin at the same time, so the next step will be to find a technique to separate both sides.”

Wysokinski added that they have ideas on how to separate each side of the coin for viewing, but the real results could come more easily once the experiment can be moved to a more powerful beamline that is under construction at the CLS and is expected to be operational within the year.

The coin experiment is only in its infancy, and after four days on the biomedical beamline, the images were not coming out as clearly as the researchers hoped. It is possible to see outlines of a figure on a few of the images  (Harvey suspects it is either an emperor or a god) and textual markings of either the Greek or Roman language. Harvey is still hopeful that eventually, the technique will be perfected and the synchrotron can start attracting archeological interest from all over the world. 

“Look at this part here,” she said, while pointing at a blurry image taken from the beamline. “This is likely the sun king, Apollo.”