Abstract

Samples of Loxodonta africana ivory were subjected to X-ray diffraction studies which showed that the hexagonal crystals have a strong preferred orientation with their basal planes perpendicular to the longitudinal axis of the tusk. Cylindrical samples were also machined from the tusk with cylinder axes along and perpendicular to the longitudinal axis of the tusk respectively. Three-point bending tests were performed on the cylindrical samples. The results show a clear anisotropy in the bending strength along the two directions. The sample with cylindrical axis longitudinally aligned shows less bending for the same applied force. The results verify a correlation between orientation of hydroxyapatite and, among other things, the mechanical strength. This may be related to the function of the tusk which with normal usage has to be able to sustain large bending forces in a direction normal to the longitudinal axis.