In 2008, archaeologists excavating a medieval refuse pit in Mainz, Germany, found a closely corroded pendant probably made within the late twelfth century. However they have been loath to open the pendant to search out out what is perhaps inside, lest they harm an already fragile artifact. Now expertise has come to the rescue. Researchers from the Technical College of Munich scanned the pendant utilizing neutron tomography, amongst different strategies, and found it contained bone splinters—probably spiritual relics, i.e., the purported bones of saints. The findings have been revealed within the interim assembly of the Worldwide Council of Museums-Committee for Conservation (ICOM-CC) Metals Working Group.

Neutron tomography, works a lot the identical approach as X-ray and gamma ray imaging strategies, besides it makes use of a neutron beam. One shoots a beam of radiation on the goal object, and a few elements work together with the pattern whereas others go by. The latter collides with an imaging goal to create what’s referred to as an attenuation sample—basically a picture of the inside of the pattern. Neutron tomography isn’t as delicate to the density of supplies as X-ray and gamma ray imaging, and in contrast to these strategies, neutrons work together strongly with very mild parts like hydrogen. So some issues simply seen with neutron imaging could also be difficult or not possible to see with X-ray imaging (and vice versa).

The strategies will be complementary and are particularly helpful for imaging archaeological or paleontological artifacts as a result of they do not harm or destroy the unique object. As an illustration, in December 2021, researchers mixed X-ray microtomography—which entails utilizing X-rays to make cross-sections of a bodily object—and neutron tomography to create a extremely detailed 3D mannequin of a 365-million-year-old ammonite fossil from the Jurassic interval, revealing inner muscle mass which have by no means been beforehand noticed. Amongst different findings, they noticed paired muscle mass extending from the ammonite’s physique, which they surmise the animal probably used to retract itself additional into its shell to keep away from predators.

The gold-plated copper pendant in Mainz measures simply 2.4 inches (6 centimeters) excessive and huge, and is within the form of a quatrefoil (a form frequent in conventional Christian symbolism). The back and front are enameled utilizing a way referred to as champlevé, which entails carving or etching troughs into the floor of a steel object after which filling them with porcelain enamel. The uncovered parts are gilded, a standard observe in medieval instances. One aspect depicts Jesus, with 4 evangelists pictured within the 4 rounded ends. The opposite aspect options Mary surrounded by 4 feminine saints.

The workforce first analyzed the floor utilizing a mix of micro-X-ray fluorescence and Raman spectroscopy to determine all the weather current. And infrared spectroscopy revealed a small pattern of beeswax. Nonetheless, “We couldn’t simply open the trailer and look inside,” mentioned Matthias Heinzel, a restorer at Leibniz-Zentrum für Archäologie (LEIZA), a part of the Technical College of Munich. “The item and, above all, the locking mechanism have been severely broken by centuries of corrosion, and opening it might imply destroying it irrevocably.”

Utilizing neutron imaging preserved the pendant whereas revealing 5 small reliquary packages of silk and linen holding bone splinters. Heinzel et al. recognized particular person parts of the pattern by triggering them with a gamma ray method known as immediate gamma activation evaluation (PGAA). “We are able to’t say whether or not or not these bone splinters are from a saint and, in that case, which one,” mentioned Heinzel. “Often relic packages include a strip of parchment indicating the identify of the saint. On this case, nonetheless, we sadly can’t see one.”

The now-fully restored pendant is at present on show on the Mainz State Museum.