The Greeks, as ever, had a word for it: 'adamantine' -- resilient, unyielding, fit to serve as a cutting edge.
Basically it means tough, hard, unyielding, rough, Adamantine was thought to be the hardest substance known, inpenetrable. Actually that's diamond, and adamantine can also be used with reference to diamond...

Having the hardness or luster of a diamond
:D

At least someone didn't know