How Underground Diamonds Are Created

Formation

• Diamonds form deep under the Earth's surface, at least 100 miles, at extreme temperatures and pressure. Temperatures exceed 3632 degrees Fahrenheit, and pressure at this depth exceeds 50 kilobars, notes GoldandSilverMines.com. As a point of reference, the pressure at sea level is one bar. One hundred miles below the Earth's surface, the weight of the overlying material is considerable, and the gravitational force of the weight is intense. These extraordinary conditions allow carbon atoms to crystallize.

Structure

• The carbon atoms that make up a diamond crystallize in a very specific way. Covalent bonds join the carbon atoms together, with each carbon atom sharing electrons with four other atoms. The resulting cubelike structure can expand in all directions, allowing the diamond to grow in size over the millions of years it spends beneath the Earth's surface.

Transportation to the Earth's Surface

• Diamonds cannot be mined at the depths at which they form. Cylindrical pipes made of igneous rocks transport the gems closer to the Earth's surface. There are two types of these pipes: kimberlite and lamproite. Both types are actually small volcanoes that bring magma and diamonds from the Earth's mantle to the surface. Kimberlite pipes are named after Kimberley, South Africa, the town in which they were first discovered. These pipes contain the vast majority of our minable diamonds. Only one lamproite pipe, the Argyle diamond pipe in Australia, has been found to contain diamonds.

Fun Facts

• Diamonds come in a wide variety of colors, with clear being the most sought after. Nitrogen causes some diamonds to have a yellow hue, while boron creates a blue hue. Pink diamonds remain a mystery to scientists, notes gemologist Diana Jarrett. Despite research, no one has yet discovered the source of the pink hue.