That detail included the distribution of organic material and previously invisible damage, which will help inform future analysis and conservation work.
The team, including researchers from Birkbeck University of London, English Heritage, Diamond Light Source, ESRF, The University of Manchester, University of St Andrews, and ISIS, looked at seven animal bones from four sites around the UK. Neutron imaging found organic matter along the outermost surface of the bones, although there was substantial variation in how organic materials were preserved throughout the bones and between samples.
The findings demonstrate that neutron imaging could be a useful screening technique to identify target areas on samples for other analysis methods, including histology or Fourier transform infrared spectroscopy (FTIR). These methods often rely on spot sampling, so choosing the right place to sample is crucial if the results are to provide an accurate description of the bone's condition.
An important source of information
Archaeological animal bones are an important source of information about how people lived and their relationships with the wider environment. They're often found as either animal remains from processes such as cooking, or worked into tools and cultural artefacts. However, the bones can be heavily damaged and degraded due to how they were handled (e.g. in cooking, use in rituals) and the environmental conditions in which they were buried, as well as how they have been stored once excavated.
Understanding how bones are preserved can help with their conservation. Importantly, type I collagen in the bone plays a key role in its mechanical properties, as well as preserving ancient DNA. Researchers use various techniques to examine archaeological bones to understand their preservation, but they all require damaging the bones to some degree. Neutrons and X-rays offer the potential for non-destructive testing. Neutrons are particularly sensitive to elements found in organic material, so neutron imaging can be used to non-invasively identify patterns of organic preservation in archaeological bone.
The team looked at cattle long bones from four archaeological sites in the UK: the Roman Corbridge Roman Town and Housesteads Roman Fort, medieval monastery Battle Abbey, and Tudor coastal gun tower Camber Castle.
Each bone had been broken during use to allow access to the bone marrow and cavity within and consisting of part of the long shaft of the bone, called the diaphysis, and the head, known as the epiphysis. For this study, the researchers focused on the diaphysis.
Chloe Pearce, a PhD student at the time of the experiment, says, “Both imaging techniques were utilised within my PhD research, and provided extensive information regarding preservation that was not accessible via more traditional, and invasive, spot analysis methods. Mapping organic inhomogeneity across entire archaeological bones has really highlighted variability both between and within archaeological sites, raising important questions regarding the reliability of pre-screening methods."
Figure 2. Neutron and X-ray tomography of archaeological bone, Roman cattle bone, excavated from Corbridge Roman Site, a major settlement near Hadrian's Wall (85-300 AD)
Organic material and hidden damage
Using neutron imaging on the IMAT beamline at ISIS to examine both longitudinal and cross-sectional distribution of organic matter in the bones, the team found organic material primarily in the surface layers of the diaphysis, although the distribution of organic matter varied across the bones. This could either be collagen or organic contaminants from the surrounding soil; it is not possible to distinguish between them using neutron imaging.
The results from neutron imaging show why spot-sampling techniques sometimes do not reflect the true preservation of the bones, as the variable preservation and localised organic content might not be detected. However, non-destructive sampling, such as neutron imaging, could help more precisely target other analyses to areas of interest.
The researchers also used synchrotron X-ray tomography on I12-JEEP beamline at Diamond Light Source, which identified hidden damage such as cracks or the effects of burning. This damage is not always visible on the surface of the bones, suggesting specimens may be more vulnerable to damage than they appear.
“This study demonstrates that combining neutron and X-ray tomography offers a powerful, non-invasive toolkit for assessing archaeological bone preservation. It challenges the reliability of traditional spot-sampling methods and highlights the need for context-aware, whole-object analysis in heritage science", adds Genoveva Burca, from Diamond Light Source.
Related publication: Non-Invasive Preservation Assessment of Archaeological Animal Bones by Complementary Imaging Techniques. Heritage 2025, 8(9), 347; https://doi.org/10.3390/heritage8090347
