Diamonds are some of the most prized gems in the world, known for their sparkling brilliance and extreme hardness. But where do diamonds come from originally? How are they formed and how can they be created in a lab? Here we’ll explore the fascinating science behind how diamonds are grown both below the Earth’s surface and above it.
Natural Diamond Formation
Natural diamonds originate deep below the Earth’s crust, formed under intense heat and pressure over billions of years. The conditions required to form diamonds only exist in limited parts of the earth’s mantle about 90-120 miles below the surface. This extreme environment squeezes carbon atoms into rigid crystal structures that become diamonds.
Ingredients: Carbon and Pressure
Diamonds consist purely of the element carbon, arranged in an isometric crystal lattice structure. To form this dense arrangement, tremendous pressure and temperature are required. At depths of over 90 miles, the pressure can be over 45,000 atmospheres (45,000 times the air pressure at sea level) and the temperature can reach over 2000°F.
Only two types of rock can provide these extreme conditions: eclogite and peridotite. As tectonic plates of the earth’s crust shift, these rocks from the mantle can be pushed up to depths shallow enough for diamond formation to occur.
Steps: Compression and Crystallization
Diamond formation takes place over long periods of geologic time in the following steps:
1. Carbon-containing minerals are squeezed under intense pressure as the rough moves upward towards the crust. This frees carbon atoms from their bonds.
2. The liberated carbon atoms are compressed into a denser form of carbon called graphite.
3. Under higher temperatures, the graphite is compressed further into rigid diamond crystals. Strong covalent bonds lock the carbon atoms into place.
4. Diamonds crystallize over billions of years, often forming in vertical columns or thin veins.
5. Magma eventually carries the diamond-bearing rock closer to the surface, where diamonds can then be mined.
Artificial Diamond Manufacturing
Above ground in carefully controlled laboratory environments, it is also possible to create artificial diamonds through advanced technological processes. The main methods are high pressure, high temperature (HPHT) and chemical vapor deposition (CVD).
High Pressure, High Temperature
The HPHT method aims to replicate the temperature and pressure conditions that form natural diamonds deep underground:
| Pressure | Over 45,000 atmospheres |
| Temperature | Over 2000°F |
To generate these extreme conditions, the process involves:
– Placing carbon source materials like graphite or diamond seeds into a hydraulic press with pistons that apply tremendous force.
– Heating the press up to over 2000°F, sometimes using molten metal catalysts.
– Maintaining these high pressure, high temperature conditions for 1-2 weeks as diamond crystals slowly grow.
The advantage of HPHT is producing diamonds with similar hardness, clarity and colors as natural diamond. The drawback is higher costs and energy use.
Chemical Vapor Deposition
The CVD method creates a gaseous carbon growth environment to deposit diamond atoms onto small seed diamonds. This lower pressure process involves:
– Placing a tiny diamond seed crystal into a vacuum chamber
– Heating the chamber to 800-1200°F.
– Introducing gases like methane and hydrogen into the chamber.
– Energizing the gases into plasma using microwaves or hot filaments, forcing carbon atoms to break free.
– Depositing the carbon onto the diamond seed in thin layers that build up to form larger diamond crystals.
– Maintaining the gas plasma for several weeks to allow diamond growth.
The advantage of CVD is lower energy requirements. The drawback is that CVD diamonds have noticeably different optical properties than natural diamonds. But advances in CVD technology are rapidly improving diamond quality.
Comparison of Natural and Artificial Diamonds
Here is a comparison between diamonds formed naturally underground versus artificially above ground:
| Attribute | Natural Diamonds | Artificial Diamonds |
|---|---|---|
| Origins | Formed deep in the mantle over billions of years | Created in a lab over weeks to months |
| Conditions | 45,000+ atmospheres pressure, 2000°F+ temperature | HPHT uses similar pressure/temperature as natural origins; CVD relies on gas deposition |
| Structure | Perfect isometric crystal lattice | Some minor structural defects |
| Hardness | Ranked 10 out of 10 on the Mohs scale | Very high hardness, but slightly less than perfectly structured natural diamonds |
| Clarity | Natural internal flaws and inclusions | Fewer flaws and inclusions than natural diamonds |
| Color | Colorless, yellow, brown, pink, blue, etc based on impurities | Usually colorless or blue when pure, can be artificially colored |
| Cost | More expensive, minimum $2,500 per carat for gem quality | Less expensive, as low as $400 per carat |
As you can see, artificial diamonds have some slight disadvantages compared to natural diamonds in terms of structure, hardness, and color. But they offset this with substantial cost savings and fewer impurities and inclusions. Artificial diamond technology continues to advance rapidly, making lab-created diamonds an affordable alternative with nearly the beauty and durability of natural diamond.
Future of Diamond Creation
Both natural and artificial diamond creation methods have room for innovation and discovery in the years ahead:
– New diamond mining technologies could reach previously unreachable depths to find larger diamond deposits. Harsher conditions could produce diamonds of exceptional quality.
– HPHT techniques are experimenting with new catalysts and carbon sources to grow diamonds faster and with fewer flaws.
– CVD technologies continue to improve diamond growth rates while lowering defects. New gas mixtures and nanofabrication techniques may enhance CVD diamond quality.
– Research into chemical processes like detonation nanodiamonds and sonication could unlock new approaches to growing tiny, uniform diamonds.
– Space exploration of Uranus and Neptune could reveal natural diamond creation from immense pressures inside the icy planets.
– Advanced future technologies like molecular nanotechnology and diamondoid engineering may make diamond synthesis trivial.
Diamonds over 4.25 billion years in the making continue to form in limited regions deep underground. Meanwhile scientists relentlessly seek new techniques to fabricate affordable diamonds above ground. The mystique and allure of diamonds will likely only grow as both natural and artificial diamond creation push the boundaries of what is possible.
Conclusion
Whether emerging over eons from extreme depths or crafted in meticulously controlled labs, diamonds encapsulate the wonder of physics, chemistry and engineering focused on a single goal: creating the world’s most brilliant and enduring treasure. Both natural and artificial methods have undergone immense refinements to provide diamonds that can adorn engagement rings, saw through concrete and shine scientific insights into crystal formation. As methods for diamond creation advance, these gems will continue dazzling our eyes while driving innovations that touch nearly every field of technology.
