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Diamonds are just carbon in its most concentrated form. That’s it — carbon, the element that makes up 18 percent of the weight of your body. In many countries, including the United States and Japan, there is no other gemstone as cherished as the diamond, but in truth, diamonds are no more rare than many other precious gems. They continue to demand higher market prices because the majority of the diamond market is controlled by a single entity.

In this article, we will track a diamond from the time it is formed to when it reaches the Earth’s surface. We will also examine the artificial rarity created by the diamond cartel, De Beers, and briefly discuss the properties of these gems.

The Origin 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. When occurring in nature, carbon exists in three basic forms.

Large diamond sitting on a rock outside

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 billions of 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 diamond’s, which makes it weaker than diamond.
  • Fullerite – A mineral made of perfectly spherical molecules consisting of 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. In order 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).

Most diamonds that we see today were formed millions (if not billions) of years ago. Powerful magma eruptions brought the diamonds to the surface, creating kimberlite pipes. On the next page, you’ll find out about these pipes.

Diamonds are not exclusive to Earth. Scientists believe that diamonds may one day be found on the moon. Samples of rock brought back from the moon indicate that carbon is 10 times more abundant in the Earth’s crust than the moon’s, according to the Artemis Project, a group whose goal is to establish a permanent moon community. But this group believes that there may be diamonds under the moon’s surface that Apollo astronauts were unable to detect. There is also some scientific evidence that diamonds may be found in larger abundance on Neptune and Uranus. Neptune and Uranus contain a lot of the hydrocarbon gas methane. Researchers at the University of California, Berkeley, have shown that focusing a laser beam on pressurized liquid methane can produce diamond dust. Neptune and Uranus contain about 10-percent to 15-percent methane under an outer atmosphere of hydrogen and helium. Scientists think that this methane could possibly turn to diamond at fairly shallow depths.

Kimberlite is named after Kimberly, South Africa, where these pipes were first found. Most of these eruptions occurred between 1,100 million and 20 million years ago.

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 are diamonds that 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.