Diamond Science

How Are Lab-Grown Diamonds Made? HPHT & CVD Explained

Real diamonds, grown from a seed in weeks. Here's exactly how the two methods — HPHT and CVD — recreate nature's process, how long it takes, and how a rough crystal becomes a sparkling gem.

Shop Lab-Grown Diamond Rings

A cut and polished lab-grown diamond by Aquamarise

Published July 3, 2026 8 min read

A lab-grown diamond isn't assembled or imitated — it's grown, atom by atom, from real diamond, using the same recipe nature uses: carbon, heat, and pressure. Scientists simply recreate those conditions above ground and speed the clock up from a billion years to a few weeks. Here's exactly how it works, in plain English.

How It's Made at a Glance

Starts with: a tiny diamond seed.
Two methods: HPHT and CVD.
Made of: pure carbon — a real diamond.
Takes: a few weeks (vs billions of years).
Then: cut, polished, and certified like any diamond.

The Short Answer

Grown from a seed, by HPHT or CVD.

Lab-grown diamonds are created by recreating the extreme conditions that form diamonds in nature. There are two methods — HPHT (High Pressure, High Temperature) and CVD (Chemical Vapor Deposition) — and both start with a small diamond seed and add carbon to it until a larger diamond crystal forms. The result is a genuine diamond, ready to be cut and set. Explore the finished stones in our lab-grown diamond rings.

It Starts With a Seed

A tiny slice of diamond.

Both methods begin with a diamond seed — a thin, flat sliver of existing diamond. This seed is the template: new carbon atoms attach to it and build up in the same rigid crystal structure, so the growing stone is diamond all the way through. This is a key reason lab-grown diamonds are the real thing, not a lookalike: they literally grow from diamond into more diamond.

Method 1: HPHT (High Pressure, High Temperature)

Recreating the earth's mantle.

HPHT is the original method, and it mimics how diamonds form deep underground:

A seed and carbon source (graphite) are placed in a growth cell with a metal solvent.
A massive press applies enormous pressure — around 1.5 million pounds per square inch.
Extreme heat (roughly 1,400–1,500°C) melts the metal, which dissolves the carbon.
Carbon crystallizes onto the cooler seed, growing a rough diamond over days to weeks.

The finished gem

Lab-Grown Diamond Rings

Handcrafted, made to order, and IGI-certified — genuine diamonds for a fraction of the mined price.

Shop Lab Diamonds

Method 2: CVD (Chemical Vapor Deposition)

Building a diamond from gas.

CVD is the newer method and dominates gem-quality production today. It grows diamond from a carbon-rich gas, layer by layer:

A diamond seed is placed in a sealed vacuum chamber.
Carbon-rich gases (like methane) fill the chamber at low pressure.
Energy (microwaves or heated filaments) breaks the gas apart, freeing carbon atoms.
Carbon settles onto the seed atom by atom, building up a diamond crystal over several weeks.

HPHT vs CVD Compared

Two roads to the same diamond.

Feature	HPHT	CVD
Recreates	Earth's mantle	Gas deposition
Pressure	Very high	Low
Grows	Around a seed in metal	Layer by layer from gas
Common for	Growing & treating	Gem-quality stones today
Result	Real diamond	Real diamond

How Long Does It Take?

Weeks, not eons.

Growing a gem-quality lab diamond usually takes a few weeks — often around one to four weeks for a one-carat stone, depending on size and method. Compare that with mined diamonds, which formed over one to three billion years deep in the earth. That speed, plus scalable production, is exactly why lab-grown diamonds cost so much less — see our price guide.

From Rough to Ring

The same journey as any diamond.

Once grown, a lab diamond is still a rough crystal. From there it follows the identical path of a mined stone: it's cut and polished by hand to maximize sparkle, then graded on the four Cs (cut, color, clarity, carat) and certified by a lab like IGI or GIA, complete with a laser-inscribed number. Only then is it set into a ring. Because it's real diamond, no one can tell it apart by eye. Learn how the labs compare in IGI vs GIA certification.

Shop Diamond Jewelry

How Lab Diamonds Are Made FAQ

How are lab-grown diamonds made?

Lab-grown diamonds are made by recreating the conditions that form diamonds in nature, using one of two methods. HPHT (High Pressure, High Temperature) presses a tiny diamond seed in extreme heat and pressure with a carbon source, so carbon crystallizes onto the seed. CVD (Chemical Vapor Deposition) places a diamond seed in a chamber filled with carbon-rich gas, which is energized so carbon atoms settle onto the seed layer by layer. Both grow a genuine diamond in weeks, which is then cut and polished like any diamond.

What is the difference between HPHT and CVD diamonds?

HPHT and CVD are two ways to grow a diamond, and both produce real diamonds. HPHT uses immense heat and pressure to mimic the earth's mantle, growing a diamond around a seed in a metal solvent. CVD grows a diamond from a carbon-rich gas at much lower pressure, building it up atom by atom. CVD is common for gem-quality stones today, while HPHT is also used to grow and sometimes to treat diamonds. The finished stones are equally genuine.

How long does it take to grow a lab diamond?

Growing a gem-quality lab diamond typically takes a few weeks, depending on the size and method — often around one to four weeks for a one-carat stone. That's a dramatic contrast with mined diamonds, which formed deep in the earth over one to three billion years. After growth, the rough crystal still needs to be cut, polished, and graded, which adds more time before it becomes a finished gem.

What are lab-grown diamonds made of?

Lab-grown diamonds are made of pure carbon — exactly the same as mined diamonds. In both HPHT and CVD, a carbon source (solid graphite or carbon-rich gas) provides carbon atoms that crystallize onto a diamond seed in the same rigid, three-dimensional structure that gives diamond its hardness and brilliance. Because it's the same carbon crystal, a lab-grown diamond is a genuine diamond, not a simulant.

Do lab-grown diamonds start with a real diamond seed?

Yes. Both HPHT and CVD begin with a tiny 'seed' — a thin slice of diamond — onto which new carbon crystallizes and grows. The seed acts as a template, so the new material builds up in the same crystal structure. This is part of why lab-grown diamonds are true diamonds: they literally grow from diamond, atom by atom, into a larger diamond crystal.

Are HPHT or CVD diamonds better?

Neither method is inherently 'better' — both produce genuine, beautiful diamonds, and quality depends on the individual stone and its four Cs, not the method. CVD is widely used for high-quality colorless gems today and can be very pure, while HPHT reliably produces excellent stones too. What matters most is buying a certified diamond and judging it on cut, color, clarity, and carat, rather than choosing by growth method.