An undated handout photo released by Rio Tinto on February 22, 2012 shows a 12.76 carat pink diamond — the largest of the rare and precious stones ever found in Australia. Picture: AFP
An undated handout photo released by Rio Tinto on February 22, 2012 shows a 12.76 carat pink diamond — the largest of the rare and precious stones ever found in Australia. Picture: AFP

A quadrillion tons of diamond. Under your feet.

DIAMONDS. A quadrillion tons of them. Beneath your feet. Ripe for the taking.

To reach them, you need to dig straight down - about 150km.

That's right into the very roots of our planet's continents.

But a diamond-rush is somewhat pointless. Not only is the depth - and heat - prohibitive, their value will likely immediately suffer immense deflation once they become commonplace.

Nevertheless, researchers from the MIT believe their presence among some of the oldest known rock can reveal much about our planet's heart.

"This shows that diamond is not perhaps this exotic mineral, but on the scale of things, it's relatively common," says Ulrich Faul, a research scientist in MIT's Department of Earth, Atmospheric, and Planetary Sciences. "We can't get at them, but still, there is much more diamond there than we have ever thought before."

Their presence was revealed after researchers discovered an anomaly in seismic data - reflected sound waves from explosions or even earthquakes that penetrate deep into the earth.

Like radar, this can be used to build up an image of what our planet's interior looks like.

It's an imposing picture.

Our continents have 'roots' - huge inverted mountains extending deep into our core.

Called cratons, they are cooler and less dense than the surrounding mantle.

But the sound waves being reflected back did not match expectations.

"The velocities that are measured are faster than what we think we can reproduce with reasonable assumptions about what is there," Faul says. "Then we have to say, 'There is a problem.' That's how this project started."

The researchers tested how fast sound travels through every kind of rock.

Only one matched what they were seeing from the Earth's core.

They believe that these cratonic roots include in their makeup some 1 to 2 per cent diamond. Given the size of known cratonic roots in the Earth, the team calculated that about a quadrillion tons of diamond are scattered within these ancient rocks, 150km to 250 miles below the surface.

That's 1000 times more diamond than previously believed.


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