Diamonds are made up of billions of carbon atoms and most were formed between one to three billion years ago, deep below the earth's surface under intense heat and high pressure.
Older than humankind itself, diamonds are one of nature’s most incredible and unique gifts. Much like a snowflake, every diamond has a natural pattern telling a different story, each one is unique and no two are alike.
What is a natural diamond?
A diamond is an amazing miracle of nature made up of billions of carbon atoms.
Diamonds have a unique cubic crystal lattice structure. Each carbon atom in a diamond is strongly bonded to four others, making them the hardest known natural substance. Diamonds also exhibit high thermal conductivity, are resistant to chemicals and have an exceptionally high transparency.
Did you know
A diamond’s melting point is 3548°C
How are coloured diamonds made?
Although extremely rare, if a diamond contains just one speck of a foreign atom that is not carbon, this can change the colour of the diamond. Discover how coloured diamonds are formed.
Did you know
Red diamonds are the rarest coloured diamond.
How are diamonds formed?
Natural diamonds can be formed in at least four completely different but equally exceptional ways, however just one of these formation processes accounts for nearly all of the diamonds we see today.
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.
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.
Did you know
The name Kimberlite derives from the South African town of Kimberley where the first diamonds were found.
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.
Another tectonic process called subduction occurs when one tectonic plate moves under another and is forced to sink, due to gravity, into the mantle. Organic carbon is recycled back into the mantle during this process and may then crystallise into diamonds.
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.
The oldest known terrestrial diamonds are thought to be about 3.3 billion years old. Our own species, homo sapiens, have only been around for 200,000 years – that’s a vanishingly small percentage of the lifetime of the diamond – so in comparison to humans, diamonds really are forever.
Not all diamonds are formed naturally. Laboratory grown diamonds or LGDs, sometimes also referred to as artificial diamonds or synthetic diamonds, are made of a man-made material that possesses the same chemical composition and the same basic crystal structure as a natural diamond.
There are two main processes for creating lab grown diamonds, High Pressure High Temperature (HPHT) or Chemical Vapor Deposition (CVD).
HPHT mimics the growth of a natural diamond by creating high pressures and temperatures that are applied to a tiny natural diamond seed upon which further diamond is grown from molten carbon.
CVD, the more commonly used process, again starts with diamond seeds. These seeds are exposed to a gas mixture that is heated to a temperature of around 3000°C in a sealed chamber. The gases then form a plasma and carbon atoms are able to stick to the diamond seed and then crystalise to form a larger diamond.
Lab grown diamonds can be manufactured very quickly - a one carat lab grown diamond can be produced in as little as three to five days. Because lab grown diamonds are mass-produced in batches, they don’t possess the enduring value of natural diamonds, and as technology continues to improve and as lab grown diamonds become more widely available their value is expected to fall.