For the first time in history, researchers were able to find a rare Earth mineral embedded in a ‘super-deep diamond.’
The rare Earth mineral, known as calcium silicate perovskite (CaSiO3), was reportedly discovered inside a super-deep diamond mined in the planet’s mantle. Surprisingly, Silicate perovskite is actually considered to be our planet’s fourth most abundant mineral.
However, while we have plenty of CaSiO3 supply, it had never been seen by humans in its natural environment. This is because it is typically buried around 650 kilometers (400 mi.) deep within the Earth.
According to the researchers, the discovery of the super-deep diamond containing the mineral is fundamental proof of the theory that blocks of oceanic crust sinking deep within our planet are being recycled into the lower mantle.
“Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth’s mantle. Discoveries of some of these minerals in ‘super-deep’ diamonds—formed between two hundred and about one thousand kilometers into the lower mantle—have confirmed part of this picture,” the researchers wrote in their study, published in the journal Nature.
Finding the Rare Earth Mineral
The super-deep diamond bearing the rare Earth mineral was found in the Cullinan mine. The mine is located on a well known diamond-bearing kimberlite pipe in the Gauteng Province of South Africa.
It is said to be the world’s richest source of rare blue diamonds and has produced over a quarter of the planet’s diamonds with a value higher than 400 carats.
“Nobody has ever managed to keep this mineral stable at Earth’s surface,” Graham Pearson, a geochemist from the University of Alberta’s Department of Earth and Atmospheric Sciences, said. “The only possible way of preserving this mineral at Earth’s surface is when it’s trapped in an unyielding container like a diamond.”
Researchers have estimated that around 93 percent of the Earth’s lower mantle is made up of silicate perovskites. However, this remained only a theory up until now. With the real mineral in the hands of scientists, they now have the opportunity to study it in detail.
The rare Earth mineral embedded in the diamond measures only 0.031 millimeters across.
Most of the diamonds here on Earth are usually born closer to the surface at around 150 to 200 kilometers deep. However, the super-deep diamond discovered by the researchers was formed at a depth of about 700 kilometers.
The pressure at that depth is approximately 240,000 times that of atmospheric pressure at sea level. The intense and crushing pressure is believed to have formed the diamond, trapping the rare Earth mineral inside it in the process.
The diamond’s structure managed to protect the CaSiO3 and prevented its crystal lattice from being deformed while the diamond moved to the Earth’s surface.
“Diamonds are really unique ways of seeing what’s in the Earth,” said Pearson. “And the specific composition of the perovskite inclusion in this particular diamond very clearly indicates the recycling of oceanic crust into Earth’s lower mantle. It provides fundamental proof of what happens to the fate of oceanic plates as they descend into the depths of the Earth.”
The researchers polished the diamond and conducted spectroscopic analysis to confirm that the mineral inside it is indeed the perovskite.
According to reports, the next phase of the study will have researchers from the University of British Columbia working on the origin and age of the diamond and rare Earth mineral.