This element, when overcome with extreme heat and pressure, creates diamonds.

The story behind the answer

Carbon is the correct answer because diamond is a crystal made entirely of carbon atoms arranged in a rigid, three-dimensional lattice (sp3 bonds). Deep in Earth’s mantle, carbon subjected to immense pressure and high temperature reorganizes from softer graphite (layered sheets) into ultra-hard diamond. The different properties come from structure—same element, new arrangement—an example of carbon allotropes.

Diamonds can reach the surface via volcanic pipes (kimberlite/lamproite). Today, we also make lab-grown diamonds using high-pressure, high-temperature (HPHT) or chemical vapor deposition (CVD) methods. Remember: C is for Carbon, Crystal, and Clear—carbon crystallizes into clear diamond under crushing Conditions. Oxygen, hydrogen, and nitrogen are vital elements, but they don’t form the diamond lattice that gives this gemstone its famed hardness.