Diamonds were mostly formed over a billion years ago at depths of 150 to 300 kilometres. At temperatures of around 1,000 degrees Celsius and a pressure of over 100 kilobars, pure carbon was pressed into a new crystal structure. The carbon atoms combine to form a regular crystal lattice and thus obtain their strength and durability.

The special temperature and pressure conditions make the difference. They are the reason why carbon becomes the hardest gemstone - the diamond - instead of just crumbly graphite.

The purer the carbon, the more valuable the diamond becomes. Under certain circumstances, additional or missing atoms in the crystal lattice can also lead to the formation of coloured diamonds.

The rough diamonds are brought near or even to the earth's surface by tectonic shifts and volcanic activity. The source rock in which the diamonds are enclosed is transported to the surface via pipes. Only then does it become accessible to humans.

Finding diamonds is very complex. Although they are found all over the world, they are rarely found in such a concentration in the source rock that mining would be worthwhile. Tons of earth have to be moved, crushed and sieved to extract one carat of diamonds.

Rough diamonds have visually nothing to do with the gemstone we know. Their surface is matt and the stone often appears milky. It is only through the cutting and polishing that a rough diamond becomes a coveted, sparkling object of desire.