What are diamonds made of?

Diamonds are made out of the element carbon. So, all the atoms in a diamond are alike. Each one is bonded to four neighboring carbons, each exactly the same distance away. Once they get put together that way, it is very difficult to move them around. So, a diamond is one of the hardest substances we have.

There are other ways to put carbon atoms together. So, we have other substances—like charcoal and lampblack and graphite—also made out of carbon. Chemists like to talk about these different forms of carbon. They show that even when substances are made from just one kind of atom, their properties depend on the way the atoms are hooked together.