Although diamond retains its title as hardest substance because of its additional ability to resist any attempt to slide, or shear, one face parallel to another, Cynn says osmium's low compressibility hints at a new class of superhard materials. (sciencemag.org)
Tooth fractures occur when dogs chew hard substances, such as hard rocks and cow hooves. (dogbreedz.com)
It's light on real die hard substance, but hell, does that really have to matterthat much? (rottentomatoes.com)