Diamond, mineral form of the element carbon, valued as a precious stone. Diamond is the hardest natural mineral and has many other exceptional properties that collectively make it an important industrial and scientific material. Unique geologically, diamonds form at great depths within Earth and are typically billions of years old.
Diamonds are crystals composed of pure carbon. In nature, diamond crystallizes from hot carbon-rich fluids. This crystallization requires tremendous heat and pressure—1000 to 1200°C (1800 to 2200°F) of heat and 50 kilobars of pressure. (One bar is based on the pressure the atmosphere exerts at sea level, about 1.02 kg per sq cm, or 14.7 lb per sq in; 50 kilobars is 50,000 bars.) The pressures and temperatures at which natural diamond forms only occur deep underground. Scientists believe that diamonds form at depths greater than 150 km (93 mi), and there is evidence that some diamonds formed as deep as 670 km (420 mi) beneath Earth’s surface.
Diamonds are crystals composed of pure carbon. In nature, diamond crystallizes from hot carbon-rich fluids. This crystallization requires tremendous heat and pressure—1000 to 1200°C (1800 to 2200°F) of heat and 50 kilobars of pressure. (One bar is based on the pressure the atmosphere exerts at sea level, about 1.02 kg per sq cm, or 14.7 lb per sq in; 50 kilobars is 50,000 bars.) The pressures and temperatures at which natural diamond forms only occur deep underground. Scientists believe that diamonds form at depths greater than 150 km (93 mi), and there is evidence that some diamonds formed as deep as 670 km (420 mi) beneath Earth’s surface.
