The Determination of Crystal Shape and Thickness in Archaeological Bone using Small-Angle X-ray Scattering Techniques (SAXS): Implications for Diagenesis

T. J. Wess¹, I. L. Alberts¹, J. C. Hiller^2,5, M. Drakopoulos³, 0. Paris⁴, A. T. Chamberlain⁵, M. J. Collins²

¹Department of Biological Sciences, University of Stirling, Stirling, Scotland, UK

²NRG Fossil Fuels and Environmental Geochemistry, University of Newcastle upon Tyne, Newcastle upon Tyne, UK

³European Synchrotron Radiation Facility, Grenoble, France

⁴Erich Schmidt Institute of Materials Science, Austrian Academy of Sciences,University of Leoben, Leoben, Austria

⁵Research School ofArchaeology and Prehistory, University of Sheffield, Sheffield,

Abstract Measures of crystallinity in archaeological bone were obtained using a variety of techniques, including Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). These measurements are intended to determine the level of change to the mineral phase of the bone specimen, when compared to the standard values acquired from modem bone. It is well known from histological observation; however, that the same bone fragment can exhibit a range of levels of preservation, from well-preserved osteons to heavily altered areas of microbial attack.

We have analyzed thin sections of modem and archaeological bone, exhibiting various levels of histological preservation, using X- ray microdiffraction at the ESRF in Grenoble, France. With 5 micron resolution attained, it has been possible to determine the thickness and shape of bone mineral hydroxyapatite crystals in localized areas of mineral modification within the same sample. Our results show that regions of bone exhibiting modified histology contain a greater dispersion of crystal shape compared to the more, well preserved regions, but that the crystal thickness is more uniform. We speculate that persistence of collagen in the archaeological bone may allow diagenetic remodeling of bone in terms of crystallite shape but defines the size of remodeled crystallites. We hope to examine the relationship between these localized results and the more bulk measurements such as FTIR and XRD, and the implications for bone diagenesis research.