As the hardest substance on Earth, diamonds are revered for their beauty and greatly sought after for their value in both jewelry and industry. They are used to cut some of the toughest and strongest materials ever created.

Natural diamonds take between 900 million and four billion years to form, while synthetic diamonds cultivated in special laboratories can be formed in just five days. The oldest diamond found to date is believed to be 3 billion years old, meaning most diamonds were created long before the dinosaurs.

Let’s take a journey into the heart of our planet and see how natural diamonds form and the synthetic production process so we can understand more about these fascinatingly beautiful gems and how they came to be.

How Do Diamonds Form

Natural diamonds are formed very deep in the Earth’s crust and require the right core element – namely carbon – and some additional environmental elements to be present in their formation and transportation to mining or even surface depths.

For diamonds to form on the Earth, several factors need to align for this to happen. Firstly, you need carbon to be present and be at depths of more than 100 miles below the surface of the Earth. Diamonds and coal are formed from the same material, pure carbon, but to form diamonds, you need massive temperature and pressure and a lot of time!

To form diamonds at this depth, the pressure needed has to be around 725000 PSI (pounds per square inch) which is approximately 467 million bar or 462 million times the air pressure on the Earth’s surface!

Diamonds also require very high temperatures to form, and they need a temperature of 2200F,  which is in a similar temperature range to that of melting steel! Now you understand why diamonds are so tough!

Diamonds form as the carbon atoms form bonds with four other carbon atoms. Under the immense pressure and temperature, the diamond’s 3 – fold symmetrical structure is created, giving these stones tremendous strength.

What Is Kimberlite Rock

Recently discovered deposits of Kimberlite rock contain ‘younger’ diamonds, thought to be only hundreds of millions of years old, but some Kimberlite deposits date back to 1,2 billion years. Kimberlite is a diamond-bearing rock that is the remnants of ancient continental crust.

These cratons formed the core of continental land masses and have remained unchanged since their formation. These magmatic layers formed at depths of around 90-100 miles below the surface and, as such, are conducive to diamond formation due to the required temperature and pressure.

Kimberlite magma pipes, where Kimberlite has been forced upwards through volcanic chimneys or pipes, are the location for most of the world’s diamond mines.

As the Kimberlite magma is forced through the narrowing magma channels, the flow velocity increases, and the diamonds ride an express elevator to the surface where hundreds of millions of years later, they were mined by humans.

Kimberlite eruptions have never been witnessed on Earth. They are thought to be the most violent and fastest-moving magma eruptions due to the release of carbon dioxide and water vapor that contribute to the incredible buoyancy of the flow.

How Are Synthetic Diamonds Formed

Scientists can replicate the temperature and pressure conditions of the deep Earth in special laboratories, and here, they can create synthetic diamonds within a few days. There are two ways to form synthetic diamonds.

The HTHP Method Of Forming Synthetic Diamonds

The first method requires exposing a piece of graphite to High Temperature and Pressure; this is known as the HTTP method. This is the most widely and commonly used method of producing synthetic stones as it is cost-effective. Here, very large presses weighing hundreds of tons are used.

First, diamond seeds are placed at the bottom of the press along with a solvent metal. This section is heated to around 2750F; this melts the metal and dissolves the high-purity carbon source in the press. As pressures of 730 000 psi are applied, this molten metal precipitates onto the diamond seeds forming a larger diamond.

Using the HPHT method, several different presses are utilized to produce synthetic diamonds, such as the cubic press and BARS Apparatus, which use slightly different approaches to create the synthetic diamonds.

The Chemical Vapor Deposition (CVD) Method Of Forming Synthetic Diamonds

In this process, diamonds are grown using hydrocarbon gas, and the temperatures and pressures in this method are significantly lower than that of the HTHP method. Typically temperatures here are around the 1400F mark, with pressures only required around the 3.9 Psi mark.

In this method, diamond seeds are placed in a chamber and then heated to around 1400F. Hydrocarbon gas is then introduced to the chamber, and under the high temperatures, the gas ionizes and breaks down to settle on the diamond seeds.

This ionization causes the gases to bond with the existing diamond, and as more gas is introduced, the crystallization continues until a rough diamond is formed. Once the diamond is created, it will be cut, polished, and then graded to be traded in the industry.

A one-carat diamond grown using the CVD method can grow in a month or less, while smaller ones need only two weeks to form fully. Infusing nitrogen into this process will produce a yellow color in the stone and speed up the crystallization process, meaning diamonds like this can be made in just 5-10 days!

Why Does It Take So Long For Diamonds To Get To Mining Depths

Natural diamonds take so long to form as the pressures and temperatures are extreme, and they are brought up to the Earth’s surface over millions of years due to very slow transportation through the Earth’s crust.

The transportation of diamonds through Earth occurs at speeds of about 30 miles per hour, as most mined diamonds are thought to have been transported by volcanic eruptions, with magma moving that speed through the crust.

What is interesting about this specific process is that if the speed is slower than 30mph, the diamond could be converted to graphite on the way. Many scientists believe that formed diamonds could be brought to mining depths in just a few hours as they are carried in the upward flowing magma.

How Is The Age Of A Natural Diamond Calculated

The conditions under which natural diamonds form are difficult to replicate, so the dating of diamonds cannot even be done by carbon dating for accuracy. This is the same method used to date fossils and other ancient materials, but it is limited to materials aged around 60 000 years.

Carbon dating uses the remaining levels of the radioactive material carbon-14 to determine the age of materials. All living beings on Earth absorb small quantities of this radioactive carbon isotope, and scientists can measure the radioactive decay level to determine the material’s age.

But, since diamonds are billions of years old, carbon dating is ineffective. Instead, scientists can calculate the age of diamonds by searching for and measuring isotopes of Rhenium and Osmium that exist in minute quantities within diamonds.

Because these elements take so long to decay from Rhenium to Osmium, around 41 billion years, they act as a kind of atomic clock in the diamond’s structural fabric, giving us amazing insight into the conditions of the environment that formed them.

Lab Vs. Mined Diamonds

While you may think mined diamonds are better, the fact is that a diamond is a diamond as they are classified under the same criteria by the Federal Trade Commission and graded the same in terms of cut, color, clarity, and carat weight.

The only benefit to you when buying lab diamonds is that they can be up to 40% cheaper than mined stones, which means you can get a larger stone at a lower price.

To tell them apart, you must be a trained gemologist with specialized equipment. Even diamond detectors cannot differentiate between them as they are chemically and optically identical.

One of the reasons that some people may opt for lab diamonds is they don’t incur anywhere close to the environmental impact that diamond mining has. For many, this appeals more to their values in procuring their stone, which has zero planetary effect.

A one-carat diamond may require as much as 176 000 pounds of dirt to be sifted before being found, and finding the right one in terms of color and clarity can take time, while lab-grown diamonds can be created with color and clarity as desired.

Conclusion

Considering the Earth is only 4,5 billion years old, some of these mined stones were formed just a billion years after the Earth was, making them very rare and special, and as they emerge from depths of more than 435 miles, they are the deepest mined materials on Earth as well.

The next time you admire those glistening diamonds in a jeweler’s window, stop and think about what it took to form them, where they came from and what it took for them to be in that window. Perhaps that will add more appreciation and wonder for these incredible gems.

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