Fig.7.

The reigning model of the packing of polycrystalline HAp platelets inside of the parallel arrays of collagen fibrils in bone¹⁷⁹: (a) HAp particles initially nucleate and grow within the gaps between N- and C-termini of collagen molecules in fibrils, but (b) either in the later stages of mineralization or in separate events they grow into the intermolecular spaces within fibrils, so that effectively between 30 and 70 % of HAp is found external to the fibrils¹⁸⁰. Despite the polycrystalline nature of the particles, the c-axis is predominantly oriented in parallel with the long axis of the fibers.