How Are Diamonds Formed?

September 27, 2023

Diamonds have fascinated humans for centuries with their brilliance and rarity. They adorn engagement rings, symbolize everlasting love, and are often associated with luxury and opulence. But have you ever wondered how are diamonds formed? These precious gems have a fascinating origin that adds to their allure.

In this article, we'll debunk a common misconception and uncover the scientific truth to understand how they move from their origin deep within the Earth to their place in our hearts.


How are Diamonds Formed : The Coal Myth

Before we dive into science, it's essential to address a widely-held myth – the idea that diamonds are formed from coal. You've probably heard the saying,'  Don't be afraid of pressure – pressure is what turns a lump of coal into a diamond.' While that's well-meaning advice, it's untrue, but its repetition throughout the ages explains why so many people believe the myth.

bituminous coal genesis of diamonds

Although both diamonds and coal are composed primarily of carbon, the similarities end there. 

Here are three scientific facts that discredit the myth:


One key reason diamonds cannot form from coal is their respective ages. Most diamonds are far older than Earth's first land-based plants, which are the source material for coal. Diamonds typically date back billions of years, while the evolution of land plants and the accumulation of plant material to form coal occurred much later in Earth's history.

Diamonds are formed deep within the Earth's mantle through a fascinating process. The question of "how are diamonds formed?" can be answered by understanding that carbon, found deep within the Earth, is subjected to incredibly high pressure and temperature conditions. These specific conditions are the key to transforming carbon into the brilliant and hard crystals we recognize as diamonds. It's worth noting that these conditions are vastly different from those required for coal formation, which primarily occurs closer to the Earth's surface.

A diamond's carbon atoms also have a different origin, often associated with ancient subduction zones and the recycling of carbon-rich materials deep within the Earth. Coal, on the other hand, originates from the accumulation of organic matter, primarily plant material.

Now, let's dive into the scientific truth of diamond formation.


The Genesis of Diamonds

Diamonds are a product of remarkable geological processes deep within the Earth. Here's a closer look at how diamonds are formed:

At the heart of diamond formation lies the carbon element. Under the intense heat and pressure in the Earth's mantle, carbon atoms arrange themselves in a crystal lattice structure, creating the diamond. The transformation takes place over billions of years and requires extreme pressure and temperatures reaching 2,200 degrees Celsius (4,000 degrees Fahrenheit). These conditions typically occur at depths 90 to 120 miles below the Earth's surface. 

Once formed, they are carried within volcanic pipes, known as kimberlite pipes, from the mantle to the surface. When volcanic eruptions occur, diamonds are brought closer to the surface, where they can be mined, cut, and polished. 

diamonds mine


Natural Diamonds: Fun Facts

Now let's look at some interesting facts about natural diamonds:

  • Diamonds are the hardest natural substance found on Earth, ranking 10 on the Mohs scale.
  • The word diamond comes from the Greek word "adamas," meaning invincible or indestructible.
  • Before the 18th century, most diamonds were mined in India. Diamonds were found in Brazil as early as 1725, North America in the 1840s, and Africa in the late 1860s.
  • Only about 25-30% of mined diamonds are considered gem quality.
  • Most diamonds used in jewelry are graded between D and Z, but diamonds come in a rainbow of colors. 
  • The Cullinan diamond, discovered in 1905 in South Africa, is the largest rough diamond ever found, weighing 3,106 carats. The finished diamond weighs 530.20 carats.


The Role of De Beers in Diamond History

De Beers is a British multinational diamond corporation founded in 1870 by Cecil Rhodes. At its peak in the 1950s, De Beers controlled over 80% of the world's diamond trade. It achieved this by consolidating its ownership of diamond mines in South Africa and other parts of the world and forming a cartel with other diamond producers to control the supply to the market.

In the 1940s, it launched the famous "A Diamond is Forever" advertising campaign, which helped to create a strong emotional association between diamonds and love. De Beers' dominance of the diamond industry began to decline in the 1980s, although it's still a major player today.


Fancy Color Diamonds

Like colorless diamonds, natural fancy color diamonds are almost entirely made up of carbon atoms. But how are diamonds formed? Deep within the Earth's mantle, under extreme heat and pressure, carbon atoms bond together to form diamonds. Over time, some of these diamonds might rise closer to the surface due to volcanic eruptions.

However, their color comes from trace amounts of other elements. For example, nitrogen within the crystal lattice gives yellow diamonds their color, trapped boron creates blue diamonds, and natural irradiation caused by alpha particles gives green diamonds their color.

Fancy color diamonds are scarce; less than 0.01% of all diamonds mined fall into the fancy color category. These diamonds are highly sought after and often cost more than a colorless diamond of the same size and quality.

fancy color diamonds


Argyle Diamonds

The now-closed Argyle diamond mine in Western Australia, which produced 90% of the world's natural pink diamonds, is a testament to the rarity and uniqueness of these gemstones. Less than 1% of the mine's production yielded natural pink diamonds.

One might wonder how are diamonds formed in nature? Diamonds are created deep within the Earth's mantle under extreme heat and pressure over billions of years. The unique conditions at certain locations, like the Argyle mine, contribute to the formation of these rare pink diamonds.

Argyle pink diamonds are known for their exceptional quality and intense color, which is attributed to the fact they come from a volcanic pipe of lamproite rather than kimberlite.


Celebrating Nature's Masterpieces

In every facet and sparkle of a diamond, there's a story waiting to be told - part of that story connects to our planet's history, and the other part is about what the stone signifies to you.

So, whether you're selecting a diamond for an engagement ring or to mark another memorable moment, let the journey of diamonds remind you of the enduring beauty that can arise from the depths of the Earth.


Leave a comment

Comments will be approved before showing up.