Small minerals make strong bones

Small can also mean strong. Huajian Gao (Max Planck Institute for Metals Research, Stuttgart, Germany), Peter Fratzl (University of Leoben, Leoben, Austria), and colleagues find that the small size of the mineral particles in bone, teeth, and nacre (mother-of-pearl) is the key to their strength, and that the same principle can be applied to the construction of artificial materials.

Bones, teeth, and nacre are all biocomposites. A protein matrix absorbs and distributes shocks, but its softness is buttressed by hard, embedded minerals. Somehow the resulting combination is a material that can be thousands of times less susceptible to fracture than the pure mineral.

Fracture of the pure mineral initiates at flaws. “It's inevitable that a mineral will be flawed,” says Gao. “No material is pure....