Deep-Earth diamonds lots more common, but microscopic, study says

Two researchers at Johns Hopkins University have developed a new model for the formation of diamonds in deep Earth, challenging the notion that the precious stones can only be created through oxidation and reduction processes.

Martial Trezzini/Keystone
A Sotheby's employee displays the rare Blue Moon Diamond during a preview at Sotheby's, in Geneva, Switzerland, Wednesday, Nov. 4, 2015.

Your diamond ring may be forever, but it probably isn’t one of a kind.

A new study from Johns Hopkins University suggests that the valuable gems are not as rare as we thought, posing a new, alternative model for the formation of diamonds.

Co-written by geochemist Dimitri A. Sverjensky and doctoral student Fang Huang, the report was published in the online journal “Nature Communications” Tuesday.

"Diamond formation in the deep Earth, the very deep Earth, may be a more common process than we thought," Sverjensky said in a statement. But this potential discovery, the study clarifies, does not mean diamonds are any more accessible, or that this new view of diamonds will have a significant impact on the gem market.

The common understanding of diamond formation relied on so-called redox reactions, possible only in specific conditions deep underground, in which fluids move through rocks in different states of oxidation. Mineable diamonds – not the deep-Earth, microscopic ones examined in the study – are transported to the surface of Earth through rare volcanic magma eruptions.

"It was always hard to explain why the redox reactions took place," Sverjensky said.

The new model that the researchers devised, however, shows that diamonds could be formed in processes much simpler than redox reactions. The new model hypothesizes that the precious stones can be created via a change in acidity when water and rocks interact, though it has yet to be proven using actual materials.

All it takes is water, Sverjensky says, to increase in acidity as it moves from one rock to another, to produce diamonds. But the resulting stones won’t exactly be suitable for earrings, let alone engagement rings. They are too small to see without a microscope.

Diamonds formed in these natural processes will also be 100 miles below the Earth’s surface, at temperatures of about 1,650 to 2,000 degrees Fahrenheit. The deepest human drilling exploration has only gone as deep as eight or nine miles, so it’s unlikely that Sverjensky nor Huang will ever get a chance to see the tiny diamonds in person.

"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."

The importance of the study, he added, is that it looks into the vital fluid movement in the deep Earth. 

In the last 25 years, there have been many studies about the prevalence of diamonds on Earth.

In fact, even without the possibility of simpler formation processes, mineable diamonds aren’t that rare. They only became a commodity in the last century or so, thanks primarily to the savvy marketing and business tactics of the DeBeers organization. For several decades, DeBeers maintained a monopolistic control over the supply of uncut diamonds, manipulating supply to meet demands so that prices would continue to rise. The company kept a large warehouse of uncut diamonds in London in order to control prices.

Nowadays, DeBeers holds about 75 percent of the diamond rough. Other suppliers are selling at similar rates, but with likely chances of the existence of several undiscovered deposits, prices might feasibly drop in the future.

“Diamonds are the hardest material found on earth. Other than that, they hold no unique distinctions,” the website says. “Among gems, diamonds are actually the most common.”

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