For the First time in History We Find Deep-Earth Mineral Inside a South African Surface Diamond

Scientists know about many things on this planet, at least in theory, without seeing them with their own eyes. Just as they recently inferred the existence of the Atlantic Sixgill Shark, they also inferred – a very long time ago – the existence of a deep-Earth mineral: the calcium silicate perovskite (CaSiO3).

The Calcium Silicate Perovskite Mineral

The calcium silicate perovskite seems to be, in theory, the fourth most abundant mineral inside the planet. It is especially prevalent in slabs of oceanic crust, plunging into the planet’s mantle at tectonic boundaries. Despite the mineral’s theorized existence and prevalence, however, not once in history did we obtain observable evidence of its existence. According to scientists, the deep-Earth mineral resides at some 700 kilometers (435 miles) below the planet’s surface. It was never observed at the surface because the mineral becomes unstable at lower depths.

However, in a study recently published in the journal Nature, geochemist Graham Pearson and his colleagues, report that they analyzed a tiny diamond (roughly 3 millimeters across) excavated from the Cullinan mines in South Africa. It was found at less than 1 km (0.6 miles) below the Earth’s surface. This is a shallow depth for both a diamond and the unstable CaSiO3, so was intriguing to the researchers. The tiny mass of calcium silicate perovskite within the gemstone became visible to the naked eye after they polished the diamond.  Further rigorous analyses, such as X-ray and spectroscopy tests confirmed that the diamond did contain calcium silicate perovskite. This was quite possibly the first intact sample ever seen.

The Cullinan Mine

The diamond the deep-Earth mineral was found inside is also a super-rare specimen. Most diamonds form at a depth of about 150 to 200 km, but this particular crystal seems to be a sample of a “deep diamond.” It most likely had been formed about 700 km below the Earth’s surface and derived from a subducted slab of ocean crust, exposed to some 240,000 atmospheres of pressure.

The Cullinan mine is once again making the headlines. It is already famous for yielding the world’s largest diamond back in 1905. Part of which now adorns the crown jewels of the United Kingdom. These days, the Cullinan mine gains a different type of notoriety. The tiny amount of calcium silicate perovskite found in the 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” (according to Professor Graham Pearson). The Cullinan Mine in South Africa produces some of the most commercially viable and valuable diamonds. It seems that the mine also provides us with scientifically interesting diamonds as well. The precious gems now offer a unique look into the deep recesses of the planet that are mostly unreachable.

Diamonds as Surface Containers

Diamonds may be the only Earth surface “containers” that can show us what happened and happens deep inside the planet. One of the only ways to keep the CaSiO3 on the surface is to trap it inside an almost indestructible and strong container like a diamond.

Diamonds are some mirror and containers for the amazing things deep inside the Earth that we cannot yet access. Back in 2014, another diamond presented the world with ringwoodite – the fifth most abundant mineral on Earth. It proved that there are large reservoirs of water in silicate rocks deep inside the mantle.

This news may act as motivation for the Japanese scientists who already want to travel to the center of the Earth. Japan’s Agency for Marine-Earth Science and Technology told CNN back in 2017 that they planned to be the first group to drill successfully into the Earth’s mantle. While the Japanese scientists want to better understand earthquakes, their drilling plan may also uncover other geological wonders that humanity would greatly benefit from. “(We want) to dig from the ocean floor to the deep, pristine mantle,” they said. However, the actual drilling will start around 2030 at the latest. Let us all hope we will see the first results as soon as possible. In the meanwhile, stay tuned. The planet seems to want to reveal its mysteries, such as this deep-Earth mineral, to us every single day.

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William E. Eubanks
 

I'm one of the main writers on the site; mostly dealing with environmental news and ways to live green. My goal is to educate others about this great planet, and the ways we can help to protect it.

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