Question

Why diamond is so hard

Answer 1

due to its tetrahederal structure

Answer 2

$<b><u><i>$ Diamond is considered as the hardest of all.

This is due to its molecular structure. Diamond is comprised of carbon atoms, and, the carbon atoms of which diamond is comprised of are very, very, tightly bound. A large amount of energy is needed to separate these atoms.

This can also be referred as a covalent bond.

Other than being the hardest substance, Diamond is one of the most expensive non metals in the world.