It has a unique crystal structure with strong covalent bonds.
Diamonds are made of pure carbon atoms that are arranged in a tetrahedral shape, meaning that each carbon atom is bonded to four other carbon atoms in a three-dimensional lattice. The bonds are very strong and rigid, and they resist breaking or bending under pressure. Additionally diamond has a high melting point and a low coefficient of thermal expansion, which means that it does not deform or melt easily when heated.
