Rare diamond
A study suggests Earth's interior is rich in diamond. Here, a rare polished diamond is pictured at the office of 77diamonds company in Antwerp, Belgium, Feb.1, 2018. REUTERS/Francois Lenoir

We all may see diamond as a rare and precious mineral, but if a new study is anything to go by, it could be much more abundant than any of us thought.

An international group of researchers — scientists from MIT, Harvard, University College London, and the University of Melbourne — has found that more than a quadrillion tons of diamonds could be hidden deep beneath the surface of our planet, way beyond anyone has ever drilled.

The team came to this theory after analyzing the movement of seismic waves or sound waves that are produced due to Earthquakes and Tsunamis and travel through the interior parts of our planet.

Several government agencies, including the United States Geological Survey or USGS, have been tracking these waves to determine the epicenter of earthquakes occurring across the globe. The data is useful for predicting life-threatening events but has also been providing new insight into the interior of our planet.

Essentially, the speed and intensity of these sound waves changes depending on the density and composition of the rocks they pass through. The information helps scientists learn more about the rocks present in Earth’s crust and uppermost mantle.

However, researchers encountered a mystery while conducting these studies — the seismic waves appear to gain speed while passing through super-old rock formations dubbed cratons.

Appearing like inverted mountains, cratons are those ancient rocks that are found in the interior of tectonic planets and extend several hundred miles deep into the mantle. Scientists have long known about these rocks and their nature, but there was no viable theory to explain the seismic wave speeds noted in the data.

“The velocities that are measured are faster than what we think we can reproduce with reasonable assumptions about what is there,” Ulrich Faul, one of the authors of the latest work, said in a statement. “Then we have to say, ‘There is a problem.’ That’s how this project started.”

To solve the anomaly, the team started working on different types of virtual rock models. They tested different compositions to find the one that could best explain the strange sound wave speeds.

As the group expected, the technique revealed that craton containing one to two percent of diamond and other deep-Earth rocks is the ideal match.

“Diamond in many ways is special,” Faul added. “One of its special properties is, the sound velocity in diamond is more than twice as fast as in the dominant mineral in upper mantle rocks, olivine.”

Considering the total volume of craton roots believed to be present in the Earth, the percentage found amounts to a quadrillion tons of diamond scattered somewhere between 90 to 150 miles beneath the surface. This is a thousand times more than what has been estimated in previous studies.

The study titled, “Multidisciplinary Constraints on the Abundance of Diamond and Eclogite in the Cratonic Lithosphere,” was published June 19 in the journal Geochemistry, Geophysics, Geosystems.