The study describes the result as an approach to improving diamond's fracture resistance without the conventional trade-off between toughness and hardness. Hardness and fracture toughness describe different properties: hardness measures resistance to deformation, while fracture toughness measures a material's ability to resist crack growth. The figure is above commonly cited hardness values for natural cubic diamond and should not be interpreted as evidence that hexagonal diamond is dramatically harder than all conventional diamond. It provides experimental evidence for millimeter-sized, phase-pure hexagonal diamond and reports hardness slightly above that of conventional cubic diamond. Potential Industrial ApplicationsNeither study demonstrates that these materials are ready to replace conventional diamond at industrial scale.