The reliable determination of bioapatite crystallinity is of great practical interest, as a proxy to the physico-chemical and microstructural properties, and ultimately, to the integrity of bone materials. Bioapatite crystallinity is used to diagnose pathologies in modern calcified tissues as well as to assess the preservation state of fossil bones. To date, infrared spectroscopy is one of the most applied techniques for bone characterisation and the derived infrared splitting factor (IRSF) has been widely used to practically assess bioapatite crystallinity. Here we thoroughly discuss and revise the use of the IRSF parameter and its meaning as a crystallinity indicator, based on extensive measurements of fresh and fossil bones, virtually covering the known range of crystallinity degree of bioapatite. A novel way to calculate and use the infrared peak width as a suitable measurement of true apatite crystallinity is proposed, and validated by combined measurement of the same samples through X-ray diffraction. The non-linear correlation between the infrared peak width and the derived ISRF is explained. As shown, the infrared peak width at 604 cm−1 can be effectively used to assess both the average crystallite size and structural carbonate content of bioapatite, thus establishing a universal calibration curve of practical use.

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The Late Bronze Age to the Iron Age transition involves profound cultural and political changes in the southern Levant. The transition is dated to the 12th century BC, based on archaeological artifacts and historical documents. A more precise absolute date for this transition for the southern Levant based on radiocarbon is difficult since the 14 C calibration curve reduces precision significantly due to wiggles that form an approximately 200-yr-long plateau. This article analyzes 14 C samples from the Late Bronze Age to the Iron Age transition at Qubur el-Walaydah. To increase the resolution of 14 C dates within the plateau, 14 C samples were collected only from well-defined multilayered contexts. 14 C dates from 11 contexts were obtained and these were analyzed using a Bayesian model that incorporated the stratigraphic information. Using this integrative approach we date the Late Bronze Age III levels at Qubur el-Walydah, containing the initial phase of locally produced Philistine pottery between 1185-1140 BC, and the Late Bronze to Iron Age transition between 1140-1095 BC.

Biogenic carbonate hydroxyapatite crystals are inherently disordered at the atomic level due mainly to the substitutions of various ions in the crystal structure, and, in the case of the bone family of materials, to the fact that these very small crystals have a very large surface‐to‐bulk ratio. Characterization of the extent of disorder is of much interest, as this relates to the stability and hence solubility of the crystals. Here the infrared spectrometry grinding curve approach developed for calcite, is adapted to carbonate hydroxyapatites. The infrared splitting factor is plotted against the full width at half height of the strong phosphate absorption peak as a function of increased grinding of the sample. By doing so, the contribution of particle size to the shape of the peaks is better separated from the contribution of atomic disorder to peak shape. It is shown that differences in disorder exist between dentine, cementum, and bone crystals which could reflect crystal size and/or atomic defects within the crystal. It is als shown that systematic differences exist between enamel samples from different taxa, which we assume only reflects atomic disorder differences within these large crystals. The method can be used to characterize atomic disorder in natural hydroxyapatites, as well as in the many different types of synthetic hydroxyapatites used for biomedical implants.

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