How the Earth's interior structure behaves has always remained a mystery, but scientists are gradually uncovering more clues as they study the composition of rocks, like the super-deep diamond recently found at Cullinan Mine, South Africa.
At first glance, the specimen appears just like any other diamond. Measuring approximately 3 millimeters across, perhaps the only thing unusual about it was its tiny size.
Moreover, its name does not seem to suit the depth at which it was excavated from, as the gemstone was ironically found just less than a kilometer below the surface. How then did it get classified as a "deep diamond?"
Tiny Diamond Contains Calcium Silicate Perovskite
After it was polished, an international group of researchers saw a strange chunk inside the diamond. They later identified it as calcium silicate perovskite (CaSiO3), the fourth most abundant mineral inside the Earth.
Although large deposits of the mineral exist in the planet's mantle, this marks the first time that it has ever been found naturally at the surface. Scientists were only able to study its nature by synthesizing a chemical duplicate.
The presence of the perovskite within the specimen indicates that the diamond was likely formed around 700 kilometers inside the planet, specifically from an ocean crust that experienced some form of collision after being exposed to an intense pressure of about 240,000 atmospheres.
"Based on our findings, there could be as much as Zetta tonnes (1,021) of this perovskite in deep Earth," says Graham Pearson, a professor at the University of Alberta's Department of Earth and Atmospheric Sciences and coauthor of the study.
More importantly, the specimen serves as proof that recycling of oceanic plates indeed occurs in the lower mantle. It also gives an insight as to what happens to these plates when they move deeper into the Earth's structure.
Results of the study have been published March 7 on the international science journal Nature.
Scientists Debate On Recycling Of Materials Beneath The Earth
Despite advancements in technology, it is still difficult for scientists to study the Earth's different layers. The farthest depth they have ever drilled to date only measures 12 kilometers. Going any further will only expose their equipment to extreme heat and pressure.
Since they are limited to using indirect methods to investigate the planet's interior, scientists can only come up with theories that sometimes conflict with each other.
Katherine Kelley, researcher and assistant professor at the University of Rhode Island, believes that the cycle of oxygen at the surface has some effect on the mantle.
However, some scientists disagree with her theory as they assert that the surface and the Earth's interior have already ceased interacting billions of years ago.