Never-Before-Seen Mineral Found Inside a Diamond

Calcium silicate perovskite (CaSiO3) is thought to be the fourth most abundant mineral on the planet, but until recently, it had never been observed in nature. Above about 400 miles beneath the Earth’s surface, this elusive mineral becomes unstable. But as Michelle Starr of Science Alert reports, researchers have found a piece of CaSiO3 that managed to make it close to the surface of the Earth, encased in a tiny diamond.

The diamond sliver was discovered at South Africa’s Cullinan diamond mine, which is best known for yielding two of the largest diamonds in the British Crown Jewels. According to Brandon Specktor of Live Science, the piece of CaSiO3 was visible to the naked eye once the diamond was polished, but an international team of researchers collaborated on analyzing the precious stone with X-ray and spectroscopy tests. They published the results of this analysis in the journal Nature.

The diamond was discovered less than 0.6 miles below the Earth’s surface, but the researchers note in the study that it was in fact a “super-deep” diamond. Most of these sparkly stones originate between 93 and 124 miles below the Earth’s surface. The one containing the CaSiO3 likely formed at a depth of around 435 miles, where the pressure is approximately 240,000 times greater than the atmospheric pressure at sea level. When this extreme force formed the diamond, the CaSiO3 was trapped inside.

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(Nester Korolev/University of British Columbia)

The diamond acted as a container, keeping a piece of calcium silicate perovskite stable as it moved towards the Earth’s surface.

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Super deep diamond found in the Cullinan mine reveals Earth minerals never seen before.

How the inner structure of the Earth behaves has always been a mystery, but scientists are gradually discovering more clues as they study the composition of the rocks, such as the super-deep diamond recently found at the Cullinan mine, South Africa.

At first glance, the specimen appears like any other diamond. Measuring approximately 3 millimeters wide, perhaps the only unusual thing was its small size.

In addition, its name does not seem to fit the depth at which it was excavated, since the precious stone was found ironically less than a kilometer below the surface. After being polished, an international group of researchers saw a strange piece inside the diamond.

Later they identified it as calcium silicate perovskite CaSiO3, the fourth most abundant mineral in the interior of the Earth. Although there are large deposits of mineral in the mantle of the planet, this is the first time that has been found naturally on the surface. Scientists could only study its nature by synthesizing a chemical duplicate.

The presence of the perovskite inside the specimen indicates that the diamond probably formed about 700 kilometers inside the planet, specifically from an oceanic crust that experienced some form of collision after being exposed to an intense pressure of around 240,000 atmospheres.

According to our findings, there could be as much as Zetta tons 1,021 of this perovskite in the deep Earth.