Lab-grown diamonds are real diamonds. They have the same chemical composition and crystal structure as mined diamonds. The difference is simply how and where they grow.
Today, most lab-grown diamonds are produced using one of two methods: CVD (Chemical Vapor Deposition) or HPHT (High Pressure High Temperature).
So, how do these two methods actually work?
How are lab-grown diamonds made?
Both CVD and HPHT start with a small diamond seed. This seed provides the crystal structure on which new diamond material can grow.
The seed is a small piece of existing diamond that gives new carbon atoms a pattern to follow. Carbon joins the diamond lattice most readily where that lattice already exists, so both CVD and HPHT start from one. Without a seed, the carbon would not organise itself into a single, well-ordered crystal.
The two methods use very different conditions to grow the diamond.
How does HPHT grow a diamond?
HPHT stands for high pressure, high temperature. The method recreates the conditions in which diamond forms deep in the Earth: carbon is dissolved in a molten metal catalyst around a diamond seed, under very high pressure and temperature, and crystallises onto the seed as new diamond. It is the older of the two methods.
- Loading the cell. A carbon source, typically graphite, is packed into a growth cell with a metal catalyst, commonly iron, nickel or cobalt, and a diamond seed.
- Pressure and heat. A press squeezes the cell to pressures comparable to those in the Earth's mantle while heating it. The metal melts and dissolves the carbon.
- Migration to the seed. The carbon source is kept slightly hotter than the seed, so dissolved carbon travels through the metal to the cooler seed and crystallises there as diamond.
- Recovery. After days to weeks the press is opened, the metal is removed and the rough crystal is recovered for cutting.
Because the crystal grows inside molten metal, HPHT rough sometimes contains tiny metallic inclusions, and specialist imaging reveals characteristic growth sectors. These are the fingerprints a laboratory uses to identify the method.
How does CVD grow a diamond?
CVD stands for chemical vapour deposition. A thin diamond seed plate sits in a low-pressure vacuum chamber filled with a carbon-rich gas, typically methane and hydrogen, heated to high temperature. Plasma breaks the gas apart, and the freed carbon atoms settle onto the seed one atomic layer at a time.
- Preparing the chamber. Seed plates are placed inside, the air is pumped out, and a controlled mixture of hydrogen and methane is introduced at low pressure.
- Igniting the plasma. Energy, commonly microwaves, turns the gas into a plasma, breaking the methane molecules apart and freeing carbon atoms.
- Layer-by-layer growth. Carbon settles onto the seed and takes up the diamond structure. Hydrogen in the mixture helps suppress non-diamond carbon such as graphite.
- Stops and restarts. Growers may pause a run to clean unwanted carbon from the crystal's edges and then continue.
As-grown CVD diamond sometimes carries a slight brown or grey tint, which is why some stones receive a post-growth treatment. Laboratories also note growth striations and distinctive fluorescence patterns under ultraviolet imaging.
Why does growing a diamond take weeks?
Because diamond only grows well when carbon is added slowly and in an orderly way. Push either process too fast and you get defects, non-diamond carbon or stress fractures instead of a clean crystal. Gem-quality stones typically grow over about 2–8 weeks, as explained on our lab-grown diamonds page.
Growth is measured in layers of atoms, so a larger or cleaner crystal simply needs more time.
What comes out of the chamber?
Rough diamond, not a finished gem. HPHT typically produces a crystal with well-defined faces, while CVD produces a flat, tablet-shaped block sitting on its seed plate. Either way, the rough is then planned, cut and polished exactly as mined rough is.
This stage decides the cut grade, which has more influence on sparkle than any other factor. Every shape we sell, from round brilliants to hearts, can be cut from either type of rough.
What is post-growth treatment, and is it disclosed?
Some CVD diamonds are put through an HPHT cycle after growth to lift a brown or grey tint towards colourless. The result is permanent and the stone remains pure crystalline carbon. Reputable laboratories such as IGI and GIA record both the growth method and any post-growth treatment on the report.
What matters is the colour grade on the report, which is assessed after any treatment. A treated CVD stone graded E is an E; the treatment is a matter of disclosure, not a hidden flaw.
How can a laboratory tell CVD from HPHT?
With specialised instruments, not with the naked eye or a loupe. Laboratories examine how the crystal grew: the pattern of growth sectors, fluorescence under ultraviolet imaging, the nature of any inclusions and spectroscopic signatures. The report then states that the diamond is laboratory-grown and, in most cases, names the growth method.
These are fingerprints of the process, not differences in what the diamond is, and the same instruments separate lab-grown from mined diamond. The girdle is usually laser-inscribed with the report number, so the stone can be matched to its certificate at any time.
CVD or HPHT: which is better?
Neither, as a category. Both produce genuine diamond, and both can produce superb stones and disappointing ones. The meaningful comparison is between two individual stones and their reports, not between two processes.
The question persists partly because some sellers promote one method as purer than the other. In practice, a laboratory grades the outcome, and the outcome is what you wear.
This is why VAALBERG's quality tiers are defined by grades rather than method: Classic (G–H, SI), Reserve (F, VS) and Signature (D–E, VVS). You can filter by these grades in our diamond search and open the report for any stone.
What should you look at instead?
The 4Cs on the report, plus a few practical details: cut, colour, clarity, whether the stone is eye-clean, fluorescence and the certificate itself. The growth method rarely changes any of them.
- Cut. The biggest lever for brilliance. For rounds, look for an Excellent cut grade; for fancy shapes, judge symmetry, polish and the stone's video.
- Colour. D–F is colourless, G–H is near-colourless and looks white in most settings.
- Clarity. VS inclusions are minor under 10x magnification. Many SI stones are clean to the eye, which is what matters when worn.
- Eye-clean. Ask whether any inclusion is visible without a loupe. Our team inspects every stone in Sweden before it ships and will tell you plainly.
- Fluorescence. Noted on the report. None to faint is the safe default; medium or strong deserves a closer look.
- Certificate. An IGI or GIA report listing the growth method and any treatment. Match the girdle inscription to the report number.
To see how these grades trade against one another at a fixed weight, browse our 1 carat diamonds. If the stone is destined for a ring, our engagement rings page walks through settings and metals.
How do CVD and HPHT compare side by side?
The table below describes how each diamond was grown, not how good it is; the individual report answers that.
| Aspect | CVD | HPHT |
|---|---|---|
| Process | Carbon-rich gas is broken down by plasma and deposited layer by layer on a diamond seed plate | Carbon dissolved in molten metal crystallises onto a diamond seed under extreme pressure and heat |
| Conditions | Low-pressure vacuum chamber, high temperature, methane and hydrogen plasma | Very high pressure and temperature in a press, with a metal catalyst such as iron, nickel or cobalt |
| Typical growth time | Weeks; about 2–8 weeks is typical for gem-quality material | Days to weeks, depending on size and quality |
| Typical characteristics noted by labs | Growth striations, possible brown or grey tint as grown, distinctive fluorescence patterns, dark non-metallic inclusions | Metallic inclusions from the catalyst, characteristic growth-sector patterns under imaging |
| Treatment disclosure | Post-growth HPHT to improve colour is common and is recorded on IGI and GIA reports | Colour treatment after growth is not typical for near-colourless material; any treatment is likewise recorded |
Frequently asked questions
Are CVD diamonds real diamonds?
Yes. A CVD diamond is pure crystalline carbon with the same hardness, structure and optical behaviour as a mined diamond. The only difference is where it grew, and the report states that it is laboratory-grown.
Is HPHT a growth method or a treatment?
Both, which causes some confusion. HPHT is one of the two ways to grow a diamond, and the same conditions are also used afterwards on some CVD stones to improve colour. A good report distinguishes the two clearly.
Will my report say whether the diamond is CVD or HPHT?
In most cases, yes. IGI and GIA reports for lab-grown diamonds record the growth method and note any post-growth treatment. Every VAALBERG product page displays the report so you can check before ordering.
Do CVD and HPHT diamonds cost different amounts?
At VAALBERG, price follows the individual stone: carat weight, cut, colour, clarity and shape, with VAT, certificate and insured shipping included. The growth method is not a pricing factor, because it does not determine quality.
Can anyone tell a lab-grown diamond from a mined one?
Not by eye, and not with a loupe. Grading laboratories use specialised instruments to identify lab-grown diamonds and their growth method, and they say so on the report. That transparency is why we only sell stones certified by IGI or GIA.
