The Origins of Diamonds
Carbon is one of the most common elements in the world and is one of the four essentials for the existence of life. Humans are more than 18 percent carbon. The air we breathe contains traces of carbon.
Temperatures can reach 1,652 F (900 C) in Archean cratons. These are common places for diamonds to form. Archean cratons are stable, horizontal geological formations created many years ago that have been unaffected by major tectonic events, according to Rex Diamond Mining Corp. These cratons are found in the center of most of the seven continents (most tectonic activity takes place around the edges).
- Diamond – an extremely hard, clear crystal
- Graphite – A soft, black mineral made of pure carbon. The molecular structure is not as compact as a diamond’s, which makes it weaker than a diamond.
- Fullerite – A mineral made of perfectly spherical molecules containing exactly 60 carbon atoms. This allotrope was discovered in 1990.
Diamonds form about 100 miles (161 km) below the Earth’s surface in the molten rock of the Earth’s mantle, which provides the right amounts of pressure and heat to transform carbon into a diamond. For a diamond to be created, carbon must be placed under at least 435,113 pounds per square inch (psi or 30 kilobars) of pressure at a temperature of at least 752 degrees Fahrenheit (400 Celsius). If conditions drop below either of these two points, graphite will be created. At depths of 93 miles (150 km) or more, pressure builds to about 725,189 psi (50 kilobars) and heat can exceed 2,192 F (1,200 C).
Kimberlite is named after Kimberly, South Africa, where these pipes were first found. Kimberlite pipes are created as magma flows through deep fractures in the Earth. The magma inside the kimberlite pipes acts like an elevator, pushing the diamonds and other rocks and minerals through the mantle and crust in just a few hours. These eruptions were short, but many times more powerful than volcanic eruptions that happen today. The magma in these eruptions originated at depths three times deeper than the magma source for volcanoes like Mount St. Helens, according to the American Museum of Natural History.
The magma eventually cooled inside these kimberlite pipes, leaving behind conical veins of kimberlite rock that contain diamonds. Kimberlite is a bluish rock that diamond miners look for when seeking out new diamond deposits. The surface area of diamond-bearing kimberlite pipes ranges from 2 to 146 hectares (5 to 361 acres).
Diamonds may also be found in river beds, which are called alluvial diamond sites. These diamonds originate in kimberlite pipes but get moved by geological activity. Glaciers and water can also move diamonds thousands of miles from their original location. Today, most diamonds are found in Australia, Borneo, Brazil, Russia, and several African countries; including South Africa, and Zaire.
Diamonds are found as rough stones and must be processed to create a sparkling gem that is ready for purchase.
