Diamonds have captured imaginations for centuries, but their origins are far more fascinating than fairy tales or red carpet glitz. Beneath their sparkle is a story of extreme forces, ancient geology, and near-impossible odds.
So, how exactly are diamonds made?
Whether you’re shopping for your first heirloom piece or just curious about what gives a diamond its magic, understanding the science behind these natural wonders adds a deeper layer of meaning to your jewelry. Here, we’ll explore how natural diamonds are formed, deep in the Earth and what makes them so enduringly special.
What Are Diamonds Made Of?
The Elemental Breakdown: Carbon at Its Purest
At their core, diamonds are made of one single element: carbon. The same carbon found in pencil graphite or charcoal, but arranged in a completely different structure. Under the right conditions, carbon atoms bond in a way that creates the hardest known natural material on Earth [1].
This atomic arrangement, called a crystal lattice, is what gives diamonds their unrivaled strength and optical brilliance [2]. So while they may feel luxurious and delicate, diamonds are, quite literally, tougher than steel [3].
Why Diamond Structure Is So Unique
It’s all about pressure and perfection. Each carbon atom in a diamond is tightly bonded to four others, forming a repeating three-dimensional pattern. This structure is what gives diamonds their famous clarity, fire, and durability, qualities that have made them symbols of lasting love, strength, and resilience.
What Makes a Diamond a Diamond (vs. Other Gems)
Unlike colored gemstones, which get their hues from trace minerals, diamonds are valued for their purity. While small inclusions are common and natural, the clearer the diamond, the more rare it becomes [4].
It’s this unique combination of simplicity (pure carbon) and complexity (precise crystal structure) that makes diamonds unlike anything else in the natural world, or the jewelry world. One of the most distinctive visual traits of a diamond is its scintillation, the dynamic play of light and flashes of colored brilliance that occur as the stone moves. While a few other gemstones exhibit some level of scintillation, diamonds are unmatched in the intensity and balance of light return, fire, and sparkle they deliver.
How Are Diamonds Formed in Nature?
Intense Pressure and Heat in the Earth’s Mantle
Natural diamonds form more than 100 miles beneath the Earth's surface, in a zone of the mantle where temperatures soar above 2,000°F and pressure is staggeringly intense. It’s here, over billions of years, that carbon atoms fuse and crystallize into the structures we recognize as diamonds [5].
These conditions are incredibly rare, which is why natural diamonds are so precious. Not every piece of carbon makes it through this metamorphosis. The Earth must deliver the right combination of depth, heat, pressure, and time.
Volcanic Pipes and Diamond Travel to the Surface
Once formed, diamonds don’t just sit in the mantle. They need a fast and forceful ride to the surface, and that journey comes courtesy of volcanic eruptions that occurred millions of years ago.
These eruptions create vertical channels of rock called kimberlite pipes. Diamonds travel upward through these pipes and cool rapidly, preserving their structure as they become embedded in the Earth’s crust [6]. It’s here, in ancient volcanic zones, that most natural diamonds are eventually mined.
Time, Depth, and Conditions Needed to Grow a Diamond
Diamonds aren’t instant creations. Some date back 3.3 billion years, nearly as old as the Earth itself [7]. Their formation is a slow, secret process, one that combines geologic violence with breathtaking precision.
The result? A gemstone that’s not just beautiful, but awe-inspiring in its very existence. Every natural diamond you see today is a fragment of Earth’s deep history made under pressure, perfected by nature.
Are Diamonds Made from Coal?
The Myth of Coal-Based Diamonds
Let’s put this classic misconception to rest: natural diamonds are not made from coal. While it makes for a poetic ide, transforming something ordinary into something extraordinary, it simply isn’t scientifically accurate.
Coal forms from decayed plant material found much closer to the Earth’s surface [8]. Natural diamonds, on the other hand, originate from pure carbon deep in the Earth’s mantle, far below where coal ever forms.
How Scientific Research Disproved the Idea
Decades of geological research have shown that diamonds predate coal by hundreds of millions of years. Most natural diamonds formed before plants even existed, meaning coal couldn’t possibly be part of the equation.
In fact, carbon in diamonds comes from carbon dioxide trapped deep in the Earth, not fossilized organic matter. So while coal and diamonds both contain carbon, their stories are worlds apart.
Where on Earth Are Diamonds Found?
Natural Diamond Hotspots Around the World
Natural diamonds are found in just a handful of places around the globe. Most come from ancient volcanic regions, where kimberlite and lamproite pipes brought these rare stones to the surface over millions of years.
Major diamond-producing countries include:
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Botswana
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Russia
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Canada
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South Africa
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Australia
Each location contributes its own story, different mining practices, stone characteristics, and histories, all of which influence how diamonds are selected and sourced.
Famous Mines and Kimberlite Zones
Some of the most iconic diamonds in the world have emerged from legendary mines like:
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Jwaneng and Orapa (Botswana) – Known for ethical sourcing and high-quality stones.
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Ekati and Diavik (Canada) – Celebrated for their commitment to environmental stewardship.
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Cullinan (South Africa) – Source of the largest rough diamond ever found.
These mines are typically located in remote, geologically rich areas where diamond-bearing rock can be carefully excavated and processed.
How Greenwich St. Jewelers Selects Responsible Sources
At G.St, we believe that a diamond’s beauty begins long before it reaches the setting. That’s why we work with designers and partners who prioritize responsible sourcing, choosing diamonds that come from trusted suppliers committed to ethical and transparent practices.
Whether it’s a timeless solitaire or a bespoke multi-stone design, we always aim to offer diamonds that not only sparkle but reflect values of integrity, artistry, and respect for people and the planet.
Explore more about our commitment to responsible materials here:
→ Diamonds & Gemstones Education
FAQs About Diamond Formation
How are diamonds naturally formed?
Natural diamonds form deep in the Earth’s mantle, where intense pressure and high heat cause carbon atoms to bond in a crystal structure. This process happens over billions of years, and the diamonds are brought to the surface by ancient volcanic eruptions through kimberlite pipes.
What type of rock turns into a diamond?
Diamonds form in igneous rocks, specifically within kimberlite and lamproite pipes—geological structures created by volcanic activity. These are the rare conduits that carry diamonds from the mantle to the crust, preserving them along the way.
Is coal under pressure a diamond?
No. Despite the myth, coal doesn’t turn into diamonds. Coal forms from plant material near the Earth’s surface, while diamonds form much deeper, from carbon sources that predate organic life.
Where on Earth are diamonds found?
Diamonds are found in countries like Botswana, Canada, South Africa, Russia, and Australia, typically in ancient volcanic regions. At Greenwich St. Jewelers, we work with designers and suppliers who prioritize diamonds that are responsibly sourced from these global hotspots.
Citations:
[1] Graphite and Diamond - Structure and Properties - https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Map%3A_Inorganic_Chemistry_(Housecroft)/14%3A_The_Group_14_Elements/14.04%3A_Allotropes_of_Carbon/14.4A%3A_Graphite_and_Diamond_-_Structure_and_Properties
[2] Structure of Diamond and Uses - https://unacademy.com/content/jee/study-material/physics/structure-of-diamond-and-uses/
[3] Is Steel Harder Than a Diamond? - https://diamond101.com/is-steel-harder-than-a-diamond/
[4] GIA 4Cs Clarity - https://www.gia.edu/gia-about/4cs-clarity
[5] How Diamonds Are Formed - https://www.capetowndiamondmuseum.org/about-diamonds/formation-of-diamonds/
[6] Kimberlites: Earth’s Diamond Delivery System - https://www.gia.edu/gems-gemology/summer-2019-kimberlites-earths-diamond-delivery-system
[7] Diamonds and Diamond Stimulants - https://nature.berkeley.edu/classes/eps2/wisc/Lect6.html
[8] Coal: What is Coal and How Does It Form? - https://geology.com/rocks/coal.shtml
