As the hardest naturally forming material on Earth, a diamond gets its name from the ancient Greek word adámas, which means “unbreakable.” But where and how is a diamond formed into this tough and beautiful substance?
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.
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. However, the temperature of the Earth varies significantly depending upon location and depth, and diamonds require a specific temperature and pressure to form. 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.
So, how do diamonds then make it from deep within the Earth's crust up to the Earth's surface? These precious gems are carried within rocks from the mantle to the surface by 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 and shaped into The World's Most Perfectly Cut Diamond.
Yet, as mentioned above, not all of the diamonds found on Earth originate here. A type of diamond known as carbonado, found primarily in Africa and South America, is believed to have been deposited on the Earth through an asteroid impact about three billion years ago. There is no scientific consensus on how carbonado diamonds originated, but many believe these diamonds formed in outer space before crashing to Earth. Diamonds can also occur in the high-pressure conditions of a crater left behind by a meteorite impact.
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