Ever since diamonds were first discovered in South Africa, they have found their way into our culture as symbols of love, status and wealth.
Despite the significance they have in our culture, most people actually don’t know much about the precious stones that adorn the jewelry we wear.
In this writeup, we look at the different ways that diamonds are formed in nature and how diamonds are made using modern technology. We’ve also created a fully animated infographic to help you visualize what happens during the various processes.
Did you know that diamonds are made of carbon and it is fundamentally the same material as pencil lead (graphite)? Yet, they are the hardest substance ever known to mankind and have completely different properties as graphite.
What gives diamond their unique properties is the covalent bonding between its atoms.
You see, when diamonds are formed under extreme temperature and pressure, atoms in their crystalline structure become tetrahedrally bonded (each carbon atom links to 3 other carbon atoms) to create a strong and stable lattice.
After years of research, geologists and scientists have a better understanding of how diamonds form in nature. It is believed that the right conditions for diamonds to be created are at elevated temperatures of 900°C to 1300°C in combination with an extremely high pressure of 650,000 psi to 850,000 psi.
In nature, there are only certain places that provide conditions like these and that’s deep within the Earth.
In fact, most diamonds form inside the Earth’s mantle under parts of the continental crust called cratons. These provide stable environments that allow diamond crystals to grow over millions of years before they make their way to the surface via Kimberlite pipes.
And it’s no coincidence that cratons are found in continents like Africa and Australia which also happen to be the biggest producers of gem-quality diamonds in the world.
Among the natural processes, this is the only method that produces diamonds large enough for jewelry as there is sufficient time for large, single-crystal stones of superior clarity and purity to develop.
When tectonic plates collide, one massive land mass is forced underneath the other into an area known as the subduction zone. If one of these plates carry rocks and materials rich in carbon content, they melt under high temperature and pressure to create diamonds.
Interestingly, diamonds formed by this process are generally small in size (between 1–80μm) and not viable for commercial use. Some of them make it back to the surface due to plate movements while others may lie in place for millions of years before being brought to the surface via volcanic eruptions.
When an asteroid strikes the Earth’s surface, the epic collision creates a massive explosion of heat and pressure on the ground. Carbon based deposits in the impact crater can get turned into tiny diamonds in an instant.
The Popigai crater in Russia is a spot which was struck by a large asteroid millions of years ago. And the immense pressure and temperature generated by the impact turned the surrounding metamorphic rocks and graphite into diamonds (less than 2mm in size).
Besides creating a spectacular sight in the night sky, meteorites also deposit their contents onto the ground when they hit the Earth’s surface. Researchers from NASA have detected large volumes of nanodiamonds in meteorites that originated from deep space.
In April 2018, the National Geographic even reported that some of these diamond-bearing meteorites could be leftover space rocks from remnants of early planets that never formed.
The first scientific breakthrough in man-made diamonds came in 1954 when General Electric developed a process that successfully replicated the conditions for natural diamond formation.
This process is called High Pressure High Temperature (HPHT) and involves the use of seed crystals which are grown in superheated anvils.
HPHT is a process that is energy intensive and has a relatively low production rate (seed crystal typically grows at a few microns per hour). During the process, the parameters need to be tightly controlled or it may cause the diamond’s growth to fail or the rough to become heavily included.
Chemical vapor deposition (CVD) is another method of making synthetic diamonds on a commercial scale. In this process, diamonds are grown in a hydrocarbon gas mixture in a controlled environment.
The hydrocarbon gas (usually methane, CH4) is heated to elevated temperatures and broken down into its atomic state. Next, the carbon atoms are then precipitated onto seed crystals and the rough diamond is grown layer by layer.
Compared to HPHT, the CVD method is relatively easy to setup and it is possible to grow synthetic diamonds over large surface areas at the same time. Besides lower temperatures, the CVD method doesn’t require high pressures and achieves higher growth rates than HPHT.
So there you have it, we’ve learnt how diamonds are made naturally and how they are created in the laboratory. But this is just the beginning of our understanding of this fascinating gemstone.
As scientists gain a better understanding of the physical world, I’m very sure they will discover more ways in which diamonds are made in nature. Also, as engineers push the boundaries of manufacturing research and development, I foresee a future in which synthetic diamonds can be made at lower costs and with better efficiency.
We truly live in exciting times. And I look forward to the years ahead where diamonds will be used as a super material to propel current technology to greater heights and drive high performance applications.
To help you visualize the various formation processes, we’ve created this infographics for an easier understanding of the concepts. Check it out below and feel free to share or embed this infographics to your website using the code below…
Like the infographic and want to share it? Feel free to copy and paste the code in the box below to your website. If you need a higher resolution image file, feel free to get in touch and I’ll generate it for you.
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Ice-VII Inclusions in Diamonds: Evidence for Qqueous Fluid in Earth’s Deep Mantle – Science Mag
‘Diamond Rain’ Falls on Saturn And Jupiter – BBC
Is Diamond Really a Super Material? – Global Spec
Synthetic Diamonds: The Industrial Supermaterial – ECN
New Diamond Nanothreads Could be the Key Material for Building a Space Elevator – Extreme Tech
Using Diamonds to Create Drug Discovery Tools – Technology Networks
Diamonds Are Made From Recycled Seabed – Cosmos Magazine