Unstable mineral found inside diamond


The mineral pirovskite of calcium silicate (CaSiO3), was for the first time found at the surface of our planet. Although this mineral is extremely abundant on Earth, occupying the fourth largest list of materials on our planet, this is the first time it is observed at the surface, since it is extremely unstable at depths lower than 650 kilometers.

The diamond in which this mineral sample is encrusted was found at a depth of only one kilometer at the Cullinan diamond mine in South Africa.

Scientists estimate that about ninety-three percent of the Earth’s lower mantle is composed of this material, but to this day the existence of CaSiO3 was no more than a hypothesis, since it had never been possible to observe it on the surface, but now and thanks to this unexpected sample, the scientists will be able to observe it in greater detail in order to better understand it.

The diamond in which the sample was found, with only 0.031 millimeters in diameter is itself also extremely rare, since most diamonds form at a rather low depth somewhere between 150 and 200 kilometers. Yet the mineral found, according to estimates, should have been formed at about 700 kilometers deep.

It was thanks to the high pressure at that depth, which is about 240 thousand times higher than atmospheric pressure at sea level, that the CaSiO3 sample was imprisoned in the diamond during its formation process, making it perfectly isolated from any external elements, preventing it from being deformed as it moved toward the surface of our planet.

The discovery also brought some information about the formation of the Earth’s mantle, since diamonds are a great source of information of this kind. The first analysis of this diamond allowed us to conclude that the inclusion of the material inside it reveals a clear recycling of the oceanic crust of the lower mantle of the Earth, clearly demonstrating what happens as the oceanic plates go down towards the interior of the Earth .

The next phase will be to try to determine the origin and age of CaSiO present in the diamond.