Science & Technology

More Than a Quadrillion Tons of Diamonds Might Be Hiding Deep Underground

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We told you before about how there are tons of diamonds in space. There are the ones that swirl around distant stars, and the ones that rain onto the surface of Neptune and Uranus. We even once told you about how diamonds created in the lab are functionally identical to those found underground. Now we're back to tell you that there's yet another needlessly elaborate way to get more diamonds than you could ever possibly need: Just dig a hole 100 miles deep.

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24-Carat Cratons

Confession time: The subtitle above doesn't make any sense. 24-karat gold refers to the purity of the precious metal, but carats are units of weight used to measure diamonds. And the weight of the diamonds we're talking about in this case is way more than a measly 24 carats. We're talking about more than a quadrillion tons of diamonds — that's a one followed by 15 zeroes. That's more than 907 quadrillion kilograms, and 4.5 sextillion (21 zeroes) in carats. And it's all hiding deep within the roots of the cratons.

What are cratons? They're the foundations of the foundations beneath your feet: the giant masses of heat-resistant stone that carry the more slippery continental plates on top. They're also incredibly deep — shaped almost like inverted mountains, their "roots" can extend as far as 200 miles (321 kilometers) below the surface. And it's in those roots that scientists now suspect an incredible wealth of diamonds is hiding.

The Sounds of Science

The catalyst for this investigation was a curious anomaly geological scientists had noticed in their seismic data. Any time a major vibrational wave passed through the roots of a craton, it seemed to move much faster than it would normally be able to. After puzzling over this problem, study leader Ulrich Faul and his team came upon a sparkling, bling-tastic solution.

First, the team developed a three-dimensional map of several seismic events and the velocities of the waves they pushed through the cratonic roots. To do so, they had to synthesize seismic data from the United States Geological Survey and other sources. Next, they developed computer models to predict how sound waves would interact with different types of rock. The results were pretty clear — only one type of stone produced the same types of velocities seen in real life. Diamonds.

Deep-Down Diamonds

According to the team's calculations, the roots of the cratons would only have to be about one to two percent diamond to produce the sound-boosting effect. There's also another good reason to suspect cratonic roots are a reliable source of diamonds: kimberlite pipes. These channels of stone are known to erupt diamonds from time to time — and they're also known to connect directly to the roots of the cratons far, far underground. In that case, it just makes sense to think that there might be a reliable source of diamond-creating pressure down at the very bottom of the bottom of the earth.

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Ever wonder why diamonds are so valuable if they're also so common? The answer lies in Matthew Hart's "Diamond: A Journey to the Heart of an Obsession." It's free if you're trying Audible for the first time. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

Written by Reuben Westmaas July 31, 2018

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