Deep in the earth

Natural diamonds were born deep below the earth’s surface in environments of extreme pressure and temperature.

At depths of over 120km, through intense heat of between 900°C and 1300°C, pressures of 45 kbar and above and over millions and often billions of years, this incredible miracle happens – carbon crystallises to form diamonds.

In order to continue this extraordinary journey, the diamonds need to be released from the intense pressure and heat under which they are formed in order to embark upon their voyage to the earth’s surface.

The Formation and Discovery of Natural Diamonds

This happens when an event deep in the earth causes a part of the mantle to melt into magma which then erupts rapidly to the surface of the earth, transporting diamonds from great depths. As the magma cools, it hardens to form the rock called kimberlite, mainly in vertical structures known as kimberlite pipes. These are the most significant source of diamonds, accounting for nearly all natural diamonds. However, of the 15% of kimberlite pipes that have been discovered across the world that contain diamonds, only 1% are economically viable, highlighting how truly rare diamonds are.

Tectonic plate movement

Some extremely small diamonds that have been found in ultra-high pressure (UHP) metamorphic rocks in Kazakhstan, China, and Norway. They are thought to have been brought to the earth’s surface by tectonic plate movement during mountain building processes.

Meteorite impact

Throughout its existence, Earth has been hit by meteorites and when there is a large meteorite impact, extreme temperatures and pressures are produced, which are the perfect environment for the formation of diamonds. Diamonds found around meteorite impact sites, e.g. the Popigai crater in Siberia, are tiny and of poor quality.

Meteorites in space

Nanodiamonds are diamonds that are a few nanometers (billionths of a meter) in diameter. Researchers have detected large numbers of nanodiamonds around newly formed stars and in some meteorites. These diamonds are too small for use; however, they are a valuable source of information about the composition and formation of our galaxy.