diamonds consist of the remains of creatures that were once alive

 

There are three main types of natural diamonds. The first is lithospheric diamond, which forms in the lithosphere layer about 150 to 250 kilometers (93-155 miles) below the Earth's surface. These are by far the most common, and probably the type of diamond you'd find on an engagement ring.

Then there are two rarer types: oceanic diamonds and ultra-deep continental diamonds. Oceanic diamonds are found in oceanic rocks, while deep continental diamonds are those that form 300 and 1,000 kilometers (186 and 621 miles) below the surface of the Earth.

And just to put that into perspective, we classify space as 100 kilometers (62 miles) above sea level, the International Space Station orbits 400 kilometers (250 miles) above Earth, and humans have never been able to drill deeper than 12.2 kilometers ( 7.6 miles). So, ultra-deep continental diamonds form... very deep in the Earth's mantle.

As expected, oceanic and continental ultra-deep diamonds look very different. Because a difference in the signature of a carbon isotope called δ13C (delta carbon thirteen) can be used to determine whether carbon is of organic or inorganic origin, previous researchers suggested that oceanic diamonds originally consisted of organic carbon previously present within living organisms. .

But in this new paper, led by Curtin University geologist Luc Doucet, the team finds that ultra-deep bituminous diamond cores have a similar δ13C composition. Surprisingly, this means that, like oceanic diamonds, this gem also contains the remains of once-living things.