From Birth to Setting:
The Diamond Story
Carbon is the fourth most abundant element in the universe and is one of life’s most important building blocks. Humans are made up of 18% carbon, diamonds however, are made up of pure carbon and are also the hardest natural material known to man.
The oldest diamonds were formed 3.5 billion years ago. At this period in time, the Earth was about 1 billion years old and the surface was an extremely inhospitable.
The Earth was formed in layers, with the outer crust varying in thickness, between 6kms and 40kms deep. The thicker crust is the land mass, and the thinner ocean crust.
Beneath the crust is the mantle and this accounts for 80% of the Earths volume. The predominant rock is called Peridotite.
Peridotite is a dense, coarse-grained igneous rock consisting mostly of the minerals olivine and pyroxene.
Whilst the upper part of the earth is ridged, the deeper parts are in a permanent state of convection, as the rock melts and cools. The heart of the earth is a liquid core of iron and nickel which is 5,500 degrees centigrade, encased within a solid inner mantle. The fixed parts of the crust are known as ‘cratons’. Under each craton is a root or keel of lithospheric mantle that can descend up to 300 kilometres deep. These areas are cooler than the neighbouring mantle at around 1,200 degrees centigrade.
A diamond will start to form and crystalise if the pressure is around 40,000 atmospheres (587,836 pounds of force per square inch). The equivalent weight would be the full force of the earth at 140km deep. The combination of these circumstances are perfect conditions for a growing diamond.
Diamonds resided in the keel for millions of years until they were expelled from their plutonic residence via enormously forceful, violent eruptions of magma around 300 to 80 million years ago. The rock, known as kimberlite, is the most abundant of the 3 types of diamond bearing magma. One of the worlds’ oldest diamond mines, in South Africa is called ‘The Kimberlite Mine’ and is mined using open cast mining methods. The powerful magma blasted through the mantel producing a cone shaped hole called a ‘pipe’. Miners slowly dig around the ‘cone’ of kimberlite and the diamond is born into our world.