The short answer: scientists start with a tiny diamond seed, expose it to extreme heat and carbon, and grow a new diamond crystal atom by atom over several weeks. The result is chemically and physically identical to a diamond that spent billions of years forming underground.
The longer answer illuminates something worth understanding — because knowing how a lab grown diamond is made changes how you think about what you're buying.
It All Starts With a Diamond Seed
Whether the method is CVD or HPHT (more on both below), every lab grown diamond begins the same way: with a diamond seed — a thin slice of existing diamond crystal, typically less than a millimeter thick.
That seed is the structural foundation on which a new diamond grows. Carbon atoms are introduced under specific conditions, and they attach to the seed's crystal lattice, extending it layer by layer into a full gemstone. The seed provides the blueprint; the process provides the raw material and the energy to build it.
This is also why lab grown diamonds aren't "copies" of a specific diamond — the seed gives the crystal its starting structure, but the new growth develops its own unique characteristics: its own inclusions (or lack thereof), its own color, its own internal fingerprint.
Method 1: HPHT (High Pressure High Temperature)
HPHT is the older of the two methods, first successfully used to grow gem-quality diamonds in the 1950s. The name tells you exactly what it does: it recreates the conditions found deep in the Earth's mantle.
Here's how it works:
A diamond seed is placed inside a growth cell alongside a carbon source (typically graphite or a compressed carbon powder) and a metal flux catalyst — usually iron, nickel, or cobalt. The entire assembly is then compressed inside a large hydraulic press and subjected to:
- Temperature: approximately 1,400–1,600°C
- Pressure: 5–6 GPa — that's roughly 50,000 to 60,000 times normal atmospheric pressure, or about 725,000 pounds per square inch
Under these conditions, the carbon material dissolves into the molten metal flux and begins to migrate toward the cooler diamond seed, where it crystallizes. The diamond grows outward from the seed, layer by layer. A typical HPHT cycle runs for 2–4 weeks to produce a rough diamond of gemstone quality.
What to know about HPHT diamonds:
- They tend to exhibit a cubic growth structure — the crystal grows outward in multiple directions
- They may contain trace metallic inclusions from the flux catalyst (iron, nickel, cobalt), which are generally not visible to the naked eye at normal clarity grades
- HPHT diamonds are often Type Ib — containing isolated nitrogen atoms (as opposed to the nitrogen clusters in most mined diamonds), which can produce a slight yellowish or brownish tint in rough form
- Post-growth high-temperature annealing treatments can improve or modify color in some HPHT stones
HPHT is well-suited for producing larger rough crystals and is commonly used for industrial diamond production as well as gemstone-grade material.
Method 2: CVD (Chemical Vapor Deposition)
CVD is the newer method and, for fine jewelry applications, generally the more versatile one. It operates at lower temperatures and pressures than HPHT, gives producers more control over the growth environment, and consistently produces the purest type of diamond crystal.
Here's how it works:
A diamond seed is placed inside a vacuum chamber, which is then sealed and filled with a carefully controlled mixture of gases — typically methane (CH₄) as the carbon source, combined with hydrogen. The chamber is heated to around 900–1,200°C, and microwave energy (or in some systems, a hot filament) ionizes the gas mixture into a plasma — a high-energy state where molecules break apart into atoms and ions.
In this plasma environment, carbon atoms detach from the methane molecules and descend onto the surface of the diamond seed. They attach to the crystal lattice one atom at a time, slowly building up a new diamond layer by layer. The process runs continuously for 2–4 weeks for gem-quality stones.
What to know about CVD diamonds:
- They grow in a layered, columnar pattern — building upward from the seed in flat plates
- CVD diamonds are almost universally Type IIa — the chemically purest classification of diamond, with essentially no nitrogen
- Type IIa is rare in nature (only about 1–2% of mined diamonds), but routine in CVD production
- This purity is why CVD diamonds consistently achieve D, E, and F (colorless) grades more reliably than mined diamonds
- CVD rough sometimes has a brown tinge from lattice strain during growth — this can usually be removed with a short post-growth HPHT treatment without affecting the stone's chemical identity
CVD's precision and controllability make it the preferred method for high-clarity, high-color stones used in fine jewelry.
CVD vs. HPHT: How Do They Compare?
Both methods produce real diamonds. The choice between them affects the stone's characteristics, not its authenticity. Here's a side-by-side view:
| HPHT | CVD | |
|---|---|---|
| Temperature | 1,400–1,600°C | 900–1,200°C |
| Pressure | ~50,000–60,000 atm | Near atmospheric |
| Growth time | 2–4 weeks | 2–4 weeks |
| Diamond type | Often Type Ib | Almost always Type IIa |
| Typical color | Can range widely | Frequently D–F (colorless) |
| Possible inclusions | Metal flux traces | Graphite, clouds |
| Best for | Large crystals, consistency | High clarity, high color |
Neither is inherently superior — they're different tools that produce excellent diamonds through different routes.
From Rough Crystal to Finished Diamond
Growing the rough diamond is only the beginning. Once removed from the growth chamber, a lab grown diamond rough goes through exactly the same process as a mined rough diamond:
1. Evaluation and planning. The rough crystal is analyzed to map its internal structure, inclusions, and optimal yield. A cutter determines the best way to shape it for maximum beauty and value.
2. Cleaving or sawing. The rough is cut into workable pieces using lasers or diamond-tipped blades.
3. Bruting. Two rough diamonds are spun against each other to shape them into a rounded, cone-like form — establishing the basic shape of the future stone.
4. Faceting. A skilled cutter polishes the diamond on a rotating wheel embedded with diamond dust, creating the precise geometric facets that determine how the stone interacts with light. This is the step that turns a rough crystal into something that sparkles.
5. Final polishing and quality check. The finished stone is inspected, cleaned, and prepared for grading.
6. Certification. The diamond is sent to an independent gemological laboratory — IGI, GIA, or another accredited body — for grading on the Four Cs (cut, color, clarity, and carat weight).
Every step after the growth chamber is identical to what happens with a mined diamond. The equipment is the same. The skills are the same. The resulting certificate is evaluated on the same scale.
The Purity Advantage, Explained
One of the most counterintuitive facts about lab grown diamonds is that the controlled growth environment often produces chemically purer stones than nature does.
Natural diamonds form in the presence of nitrogen — it's everywhere in the Earth's mantle environment. Most mined diamonds trap nitrogen clusters in their crystal structure during formation, making them Type Ia stones. This is responsible for the slight warmth in color that affects most diamonds on the market.
CVD lab grown diamonds form in a gas environment where nitrogen is deliberately excluded. The result is Type IIa — diamonds with essentially no nitrogen impurities. Type IIa diamonds are exceptionally colorless and represent the very top of the natural color spectrum. In nature, they're extraordinarily rare. In a CVD lab, they're the norm.
This doesn't make lab grown diamonds "better" than mined diamonds in some absolute sense. But it does mean that when you're comparing stones on paper, a D-color lab grown CVD diamond is every bit as pure and colorless as a D-color mined diamond — often more so.
Why Does the Process Matter to You as a Buyer?
Understanding how lab grown diamonds are made helps you understand a few practical things:
Inclusions are normal. Just as mined diamonds have inclusions, lab grown diamonds can too — the types are slightly different (metallic traces in HPHT, graphitic marks in CVD vs. mineral crystals in natural), but a VS1 or VS2 graded stone looks clean to the eye regardless of origin.
CVD and HPHT are both legitimate. Neither method produces an inferior diamond. They produce different types of diamonds. Your IGI or GIA certificate will indicate the growth method — but both result in a certified, real diamond.
The timeline is compressed, not the quality. Growing a diamond in weeks rather than billions of years doesn't diminish it — it's the same fundamental process, accelerated through technology rather than geological time. The crystal structure that results is identical either way.
What you end up with is a stone that sparkles like a diamond, tests like a diamond, and grades like a diamond — because, by every scientific and legal measure, it is one.
Continue learning: What Is a Lab Grown Diamond? | Are Lab Grown Diamonds Real? | Lab Grown vs. Natural Diamond
