Ancient Diamonds Came From Seawater and Future Diamonds Might Come From The Air

Cloudy diamonds give some scientists new clues to how they formed underground, others find ways to make them out of thin air.

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They may not be fit for a ring, but microscopic diamonds found in a mine in Canada’s Northwest Territories could be the key to uncovering how the stones form.

It’s pretty well-known that diamonds are formed when carbon is compressed at extremely high pressure inside the earth’s crust. But while time and pressure are important, the gems still form like other crystals, which need a reactive fluid for grow in. Now, a group of researchers say they have uncovered evidence that points to some kinds of diamonds crystallizing in pockets of seawater trapped about 124 miles below the earth’s surface.

"I think it really helped to get the diamond forming reaction going," Graham Pearson, a geochemist at the University of Alberta who co-authored the study, tells Emily Chung for CBC News. "We would argue having some seawater and brine helps formation because it's a very reactive fluid."

The bold conclusion comes from data taken from 11 microscopic diamonds with millions of droplets of fluid suspended within them. When crystals form rapidly, they can sometimes trap pockets of liquid inside themselves. The liquid is often the same reactive fluid that the crystal grew in, leaving clues as to how the gem was formed. Using an analysis technique called spectroscopy, the scientists scanned the tiny, cloudy diamonds for clues of what chemicals the droplets were made of, Chung writes. What they found was water.

"It's really diamond formation caught in the act," Pearson tells Chung.

To get a more detailed chemical analysis, the researchers used lasers to vaporize the diamonds. They discovered that the trapped bubbles of water contained high levels sodium and chlorine – the building blocks of salt – as well as strontium, which is strikingly similar to what would have been found in seawater hundreds of millions of years ago, Chung writes.

Pearson believes that the diamonds may have formed when seawater was pushed under the earth by the movement of tectonic plates, where carbon-rich rocks and high pressure would have made the perfect conditions to grow diamonds. While it’s still unclear how these microscopic, cloudy diamonds are related to the one on your co-worker’s flashy engagement ring, it does give scientists new hints to how water and carbon cycle through the earth.

While some scientists are figuring out how diamonds are made beneath the earth over millions of years, others believe they’ve found a new way to make artificial diamonds out of air pollution. A group of researchers from George Washington University announced at a recent meeting of the American Chemical Society that they have devised a method for extracting raw carbon from the atmosphere, Daniel Cooper writes for Engadget.

In a new study published in the journal Nano Letters, the researchers say they have extracted carbon nanofibers from carbon dioxide through an electrochemical process. Carbon nanofibers are strong and lightweight materials typically used in machinery like cars and airplanes, and could also be refined into artificial diamonds for jewelry and electronics. However, while the nanofibers are versatile, they are extremely expensive to make. By sticking a pair of electrodes in a bath of lithium carbonate and lithium oxide, the researchers say they were able to extract carbon straight out of the atmosphere, which could provide manufacturers with a reservoir of cheap nanofibers.

If this system could be made to work on a large scale, it might not just make carbon nanofibers easier to get, but could help to actively reduce the carbon in the atmosphere and global warming, Mike Orcutt writes for the MIT Technology Review. However, it has a ways to go: not only is the technology still in its infancy, but the current demand for carbon nanofibers is nowhere near what would be necessary to put a dent in carbon dioxide levels.

While diamonds made from the sky might help the environment in the future, jewelers will still have to rely on old-fashioned ground diamonds for now.

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