Why Blue Diamonds Are So Precious To Scientists

In the Majaian “Diamond Sutra”, dating from AD 868, diamond is the material with which “to pierce through worldly illusion to illuminate what is real and eternal.”

But perhaps the most poetic were the ancient Greeks, for whom diamonds were tears cried by the gods or shards of fallen stars.

The wonderful thing is that the truth about diamonds is almost as extraordinary as all those beliefs.

They are made of the element that is the basis of life itself: carbon.

Extraordinarily tough, they can withstand enough pressure to recreate the extreme conditions in which they were born; and yet, subjected to the correct combination of heat and oxygen, will disappear in a puff of carbon dioxide.

In addition to its extraordinary luster and brilliance, the diamond it is the most rigid material, the best thermal conductor with extremely low thermal expansion, chemically inert to most acids and alkalis, transparent from deep to visible ultraviolet and far infrared rays, and is one of the few known materials with negative electronic affinity .

They form naturally in a few places on Earth: in the depths of continental cratons or in the impact of a meteorite.

Y come to the surface in an explosive manner, in the magma of some of the strangest eruptions in history, of the few volcanoes that have their roots deep in the planet.

Not all diamonds are transparent or slightly yellow or brown, like the ones we generally imagine.

There are also colored ones and they are called “fantasy”: red, blue and green are the rarest, and orange, purple, yellow and yellowish green are the most common.

But all, once formed, have a unique ability to house and protect any mineral contained within their crystalline structures, giving scientists a special sample of the mantle mineralogy and a glimpse of conditions miles below. of the planet’s surface.

And in that sense, the blue diamond is exceptional.

Most diamonds are formed at depths of about 150 kilometers under the continents.

The blues originate up four times deeper, in the mantle inferior from the earth.

That was only discovered in 2018 as these gemstones “are tremendously expensive, making it difficult to access them for scientific research purposes,” explained the study’s lead author. who revealed it, geologist Evan Smith of the Gemological Institute of America.

Not only are they valuable, they tend to be very pure, so they tend to have no “inclusions,” or small pieces of non-diamond material, minerals that were in close proximity when it was being formed.

Those imperfections give scientists more information.

But they managed to analyze 46 blue diamonds with inclusions, and determine their origin between 410 and 660 kilometers deep.

Several of the samples even showed clear evidence that they came from more than 660 kilometers, meaning they originated from the lower mantle.

That turns them into true time capsules, containers of information that is almost impossible to find.

“We can’t get to the interior of the Earth. Diamonds form there and usually encapsulate whatever is down there,” George Harlow, geologist and curator of the Gem and Mineral Rooms at the American Museum of History, told BBC Reel. Natural in New York.

“They are like our space probes. Eventually, some make it to the surface of the Earth so that we can study them.”

An example of the clues they have given us?

Blue diamonds were, for most of history, a mystery. It was unknown why they were that beautiful color.

It was finally discovered that it was because contained traces of boron, a metalloid chemical element that can enter the lattice structure of a diamond during its growth.

But once that mystery was uncovered, an enigma emerged.

If blue diamonds are formed in the Earth’s mantle, while boron is concentrated in the crust. Then,where did these diamonds get their boron from?

The answer to that geochemical puzzle would give us clues about the depths of our planet.

The hypothesis put forward by the Smith-led research group is that boron came from the seafloor and was transported toward the Earth’s mantle when one tectonic plate slid under another, a process known as subduction.

By incorporating minerals rich in water, it was able to extend deep into the seafloor, even into the mantle portion of the oceanic plate.

Discovering traces of boron in diamonds that are born at such a distance from the Earth’s surface reveals that minerals that contain water travel much deeper into the mantle than previously thought, which indicates the possibility of a super deep hydrological cycle.

As Harlow puts it, blue diamonds “are not only beautiful and rare, but extremely interesting. They teach us a lot about our planet.”

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