The hardest minerals in the world—diamonds—are made from one of the most common element: pure carbon. But here’s the strange thing. Graphite—one of the softest minerals in the world—is also made of pure carbon. What makes diamonds and graphite different is the way the carbon atoms are arranged. The carbon in graphite is arranged in micro-thin sheets, making the dark gray graphite so soft that it leaves a mark when dragged across a surface. (That’s why graphite is used to make pencil lead). Diamonds, however, are formed under intense pressure hundreds of miles below Earth’s surface. The powerful bonds forged by their carbon atoms have a cubic crystal structure. That structure keeps diamonds stable and solid while hot magma is being formed into igneous rock around them.
