What element is a diamond composed of?

A diamond is composed of carbon. It is a crystalline form, or allotrope, of the element carbon, with each carbon atom covalently bonded to four neighboring carbon atoms in a rigid three-dimensional lattice.

That structure explains diamond's exceptional hardness, transparency, and thermal conductivity. Graphite, graphene, and diamond are all made from carbon, but their atoms are arranged differently. Graphite forms layered sheets that slide easily, while diamond forms a tightly connected network.

Natural diamonds crystallize deep in Earth's mantle under immense pressure and high temperatures, then reach the surface through rapid volcanic eruptions. They do not usually form from coal, a common misconception; most diamonds are far older and formed in geological settings unrelated to ordinary coal deposits.

Small amounts of impurities can affect a diamond's color. Nitrogen may produce yellow tones, while boron can create blue diamonds. Laboratory-grown diamonds are also carbon crystals, so their origin differs from mined diamonds but their basic composition is essentially the same.