Neutron Imaging Reveals Tiny Bones Inside 800-Year-Old Pendant

The high-tech method allowed researchers to examine the artifact without opening it

800-year-old pendant from Mainz
The 800-year-old pendant is made of copper and plated in gold. Sabine Steidl / LEIZA

In 2008, archaeologists in Germany were thrilled to discover a mysterious gold-plated pendant in a medieval trash heap. They suspected it was a rare storage container for religious relics, called a phylactery, that owners often wore around their necks. But without looking inside, they couldn’t know for sure.

They spent 500 hours clearing centuries of corrosion and grime from the gilded copper pendant, but the artifact’s advanced age and delicate condition made it difficult to study much further. They feared that if they opened the quatrefoil-shaped pendant, they’d damage it beyond repair in the process.

The archaeologists first took X-rays to see if they could get a glimpse of what was inside, but that technique didn’t reveal much.

They finally achieved success with neutron tomography, a high-tech method that uses neutrons to create 3-D images of objects without damaging them.

Quatrefoil shape on turquoise background
Neutron tomography helped reveal the pendant's contents. Burkhard Schillinger / MLZ

Inside the pendant, they found five textile packets made of silk and linen, held together by a thin thread, that contained tiny bone fragments. The researchers don’t know who the bone splinters belonged to, or whether that person was a saint.

“Usually relic packages contain a strip of parchment indicating the name of the saint,” says Matthias Heinzel, a restorer with Leibniz-Zentrum für Archäologie, in a statement from the Technical University of Munich. “In this case, however, we unfortunately can’t see one.”

Researchers presented the discovery at a September meeting of the International Council of Museums-Committee for Conservation’s metals working group.

Covered in images of Jesus, Mary and other religious figures, the pendant measures 2.4 inches tall by 2.4 inches wide; it’s less than half an inch thick. Dating to the late 12th century, it was likely made in a workshop in Hildesheim, a city in northern Germany in the state of Lower Saxony. It also features a locking mechanism.

Gray quatrefoil shape on a black background
Researchers discovered five packages made of silk and linen inside. Burkhard Schillinger / MLZ

Researchers found it 14 years ago while excavating the historic Old City section of Mainz, a city in western Germany situated along the Rhine River.

Only three other known phylacteries of this type from the Hildesheim workshop exist—the others are located in Boston, Rome and Halberstadt, Germany. 

Thanks to the non-damaging imaging techniques, the pendant is still in one piece. It’s now on display at the Mainz State Museum.

“We consider it our duty to preserve the object in its historical authenticity as completely as possible for future generations, and to leverage the modern opportunities of non-destructive investigation,” says Heinzel in the statement.