How and where are diamonds formed?
Diamonds are formed between 120 and 200 kilometres (75-120 miles) under the surface of the earth. According to geological estimates, the first formation of diamonds was approximately 2.5 billion years ago, while the latest was 45 Million years ago – really an incredibly long time! According to modern geology, the carbon which creates diamonds is made by the melting of natural, rock in the upper mantle of the Earth. There is a wealth of carbon at this depth. Changes in temperature in the upper mantle force the carbon to sink, where it melts and eventually returns to rock, as it cools. If pressure, chemistry and temperature come together in just the right way, the carbon atoms in the molten rock bond, and this creates diamonds.
There are no guarantees that these deposits of carbon will become diamonds. Things can go wrong: if the pressure drops or the temperature rises, the diamond crystals could melt or dissolve entirely. Even if they form, often it can take many thousands of years for the stones to come close enough to the Earth’s surface to be mined or gathered.
Diamond's journey to the surface?
Diamond deposits are known as Blue Ground or Kimberlite Pipes. These are known as Primary Mines. Diamonds can also be found in river beds, and these are Alluvial Deposits.
We can now appreciate that it takes many, many years of hard work on the part of Mother Nature to create these extraordinary gems. When you hold a diamond, a piece of history is in your hands. It has been made under just the right conditions by purely natural processes and extracted from the depths of the Earth, not crafted by a factory. Each one is unique. Interestingly many mined diamonds do are not made into jewellery. Only a quarter of mined diamonds are made into jewellery. 100 tons of earth and mud need to be processed to mine just one carat of diamond, and not even necessarily in a single stone: it might be anything from 0.005 ct to 1 ct.
This image is an example of an uncut diamond. The specimen in the picture is a particular style of stone is known as ‘Glassy’, the term for an uncut diamond which emerges from a mine clean, and requires no polishing, a very rare quality. Diamonds can come in several rough shapes. This one is 8-sided or octahedral. So the next time you glance at your diamond, don’t forget to consider the amount of, labour, energy and time which have been required to create it.