Diamonds

Humans are 18% carbon an element which in its most concentrated form becomes those precious gems.

Diamonds form in the molten rock of the Earth's mantle, about 160 kilometres below the surface of the planet. They are created when carbon is placed under a minimum pressure of 435,113 pounds per square inch (psi), at a temperature no cooler than 400 degrees Celsius. Which is why conditions are perfect way, way down underground, where pressure builds to about 725,189 psi, while the heat can exceed 1,200 C.

The formation process is not a rapid one, and most of the diamonds we see today were created millions, or even billions, of years ago, and then brought closer to the Earth's surface by eruptions of magma. These powerful volcanic bursts cooled and formed conical veins in the ground called kimberlite pipes (named for Kimberly, South Africa, where they were first found), which are mined for the gems within.

Diamond can also be discovered in river beds, to where they have been moved from kimberlite pipes by geological activity. Movement of glaciers and water can carry the gems thousands of miles from their points of origin.

But diamonds may not be exclusive to the third rock from the sun, where they are found in Australia, Borneo, Brazil, Russia and many African countries. Samples of rock brought back from the moon have led astronomers to postulate that one day the gems will be found on our planet's satellite.

The moon appears to be ten times richer in carbon than the Earth's crust, meaning there may be diamonds under the surface. However, Apollo astronauts were unable to detect the gems, and the cosmic information is from a group called the Artemis Project, which aims to establish a human colony on the moon.

Back on Earth, diamond is the hardest known natural substance. This is thanks to its molecular structure of carbon atoms linked together in a lattice structure. Each of the atoms shares electrons with four other carbon atoms. This is called tetrahedral bonding, which forms a super-strong molecule.

This hardness is why another diamond or a laser has to be used to split raw diamond rock into smaller pieces, which are finished (again using another diamond as a tool) and polished before they are sold on to dazzle jewellery shop customers.