Diamonds May Be Common, Deep in the Earth

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Diamonds may not be as scarce as thought, as a new study suggests they can form in a previously unknown way deep underground. Tyrone Siu / REUTERS

Diamonds are not exactly as rare as you may think. New research suggests that they can form through a previously unknown reaction, and they may be widespread in the rocks far beneath our feet.

"Diamond formation in the deep Earth, the very deep Earth, may be a more common process than we thought," said Johns Hopkins University geochemist Dimitri Sverjensky, in a statement.

In a study describing the work, published in the journal Nature Communications, Sverjensky and co-author Fang Huang explain that their model suggests diamonds can form when water flows between different types of rocks as its acidity naturally decreases and reacts with the rock, while under extreme pressure and heat. It was previously thought that diamonds only formed through the oxidation of methane or the reduction of carbon dioxide. But this study suggests neither gas is necessary.

It’s a theoretical calculation, however, and cannot be tested with current technology, as all of this is thought to take place 90 to 120 miles below the surface if Earth, where temperatures are about 1,650 to 2,000 degrees Fahrenheit. To date, the deepest any humans have drilled is eight to nine miles below the surface, according to Sverjensky.

Also, don’t expect this to have any effect on diamond prices. For one, diamonds formed this way would be tiny and impossible to see with the naked eye. Secondly, they are deep, deep in the Earth. The diamonds you see on engagement rings are only up here because rare types of magmatic eruptions will occasionally bring them to the surface.

This adds to recent findings of diamonds in other unexpected places. "The more people look, the more they're finding diamonds in different rock types now," Sverjensky said. "I think everybody would agree there's more and more environments of diamond formation being discovered."

It should also be noted that diamonds are not actually very rare, at all. Big companies control the supply of diamonds, creating an artificial sense of scarcity and ramping up demand. As explained in The Washington Post:

This practice was born in the diamond fields of South Africa in the 1880s, when Cecil Rhodes, the chairman of De Beers Consolidated Mines, discovered that he could inflate prices at will simply by locking up the rights to every diamond mine he could find. His successor, Ernest Oppenheimer, developed a complex network of wholesalers that gave De Beers effective control of up to 90 percent of the world's rough-diamond trade through most of the 20th century, as the company hoarded stones in basement vaults and doled them out strategically.

Though other companies have entered the game and driven down De Beers market share, stockpiling and artificial scarcity still keep diamond prices high.