Give reasons:

Diamond is used as an abrasive.

In diamond, carbon is sp³ hybridized. Each carbon atom is bonded to 4 other carbon atoms with the help of strong covalent bonds. These covalent bonds are present throughout the surface, giving it a very rigid 3-D structure. It is very difficult to break this extended covalent bonding and for this reason, diamond is the hardest substance known. Thus, it is used as an abrasive and for cutting tools.