A series of human cortical bone specimens has been heated to temperatures up to 1200°C and the mineral content examined in detail by X-ray diffraction. Line profile analysis of the diffraction data has been undertaken to characterise the microstructural (crystallite size and microstrain) features of the mineral at each temperature. Individual profile fitting of several maxima from each diffractogram has also provided precise lattice parameters of the apatite at each temperature.

The apatite did not show any significant decomposition over the temperature range although CaO was increasingly formed at temperatures above 600°C. Both finite crystallite size and microstrain contributed significantly to the diffraction peak broadening below 600°C. When heated to >800°C, the small, rod-like mineral crystallites changed from a highly anisotropically strained state to one with significantly larger equidimensional crystals possessing little microstrain.

The findings are discussed in the context of graft bone substitutes and surgical heating of bone.