Give reasons: Diamond is used as an abrasive.

(N/A) In diamond,each carbon atom is $sp^{3}$ hybridized and bonded to four other carbon atoms through strong covalent bonds. These bonds extend throughout the crystal lattice,creating a highly rigid $3-D$ network structure. Due to this extended covalent bonding,diamond is the hardest known natural substance,making it suitable for use as an abrasive and in cutting tools.