Carbon has two unique features that make it a remarkable atom for life.
The first is its bonding structure, which allows it to form 4 single covalent bonds equally in all 3 dimensions. This makes covalent bonds of equal strength and distribution in all 3 dimensions, which means any forces applied to diamond are distributed equally in all directions so there is no weakness in shear forces, twisting forces, tension, or compression. In every case, the forces are equally balanced making diamond exceptionally strong. However, when diamond does break it does so suddenly as all the bonds snap at about the same time, usually severing or shattering this crystal. When pure carbon is compressed with lesser force, it becomes graphite .