Diamond is the hardest natural material that is known, its hardness set to 10, i.e. hardest, on Mohs scale of mineral hardness and having an absolute hardness value of between 90, 167, and 231 gigapascals in various tests. Diamond's hardness has been known since antiquity, and is the source of its name. However, aggregated diamond nanorods, an allotrope of carbon first synthesized in 2005, are even harder than diamond.
The hardest diamonds in the world are from the New England area in New South Wales, Australia. These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds. Their hardness is considered to be a product of the crystal growth form, which is single stage growth crystal. Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice all of which affect their hardness.