As the hardest naturally forming material on Earth, a diamond gets its name from the ancient Greek word adámas, which means “unbreakable.” This tough and beautiful substance is made of pure Carbon atoms, which form stable bonds in a three-dimensional crystalline structure.
The formation of a diamond actually requires very specific conditions – conditions that are met in only two places on Earth. The first is in the Earth's crust, in the lithospheric mantle below relatively stable continental plates. The second is at the site of a meteor strike probably carrying diamonds from another planet crust.
The lithospheric mantle constitutes the Earth's crust and uppermost mantle, which makes up the hard and rigid outer layer of our planet. This is where the most common formation of a diamond occurs, as diamonds begin to form deep inside the great depths of this mantle, about 87 to 190 miles down (140 to 300 Km). However, the temperature of the Earth varies significantly depending upon location and depth, and diamonds require a specific temperature and pressure to form (pressures exceeding 70, 000 kg/cm3 and the temperatures higher than 13 000 C). Therefore, the necessary temperature and pressure to form a diamond is found only at certain depths in the ancient, thick, and stable parts of continental plates. In addition, the longer a diamond lies deep down in a stable part of a continental plate, the larger it grows.
Diamonds move from deep within the Earth's crust up to the Earth's surface by being carried within rocks dunring deep-origin volcanic eruptions. Because the volcanic shift must occur deep enough to carry the diamond up from where it has been forming, such eruptions are a relatively rare occurrence.
Once a diamond has been carried up to the Earth's surface by a volcanic eruption, it may erode out of the rock that carried it up so that it can be discovered.
Every year, approximately 130,000,000 carats (1 carat being 0.2 gr) of diamonds are mined, with a total value of nearly $9 billion USD. Diamond mines are concentrated in a small number of locations around the world, and the diamond supply chain is controlled by a few powerful businesses. Indeed the top 5 players accounted for 70% of total volume of production in 2013.
Roughly 49% of those diamonds are found in Central and Southern Africa, although significant diamond sources have been discovered in other areas throughout the world, including India, Canada, Brazil, Russia, and Australia. The five countries with the highest producing diamond mines are Botswana, Russia, Democratic Republic of Congo, South Africa, and Canada. These countries account for more than 75% of total diamond production by weight. The diamond mine that produces the most diamonds in the world is Jwaneng, which is located in Botswana and produced 11.5 million carats of diamonds in 2009.
BAIN REPORT The Global Diamond Report 2014
BAIN REPORT The Global Diamond Report 2013
Earthly origins of diamonds at heartsonfire