HPHT vs CVD Lab-Grown Diamonds: quick comparison
HPHT and CVD are the two methods used to grow diamonds in a laboratory. Both produce real diamond — carbon in the diamond crystal structure, with the same hardness, the same optical properties and the same grading scales as a mined stone. Neither is a simulant.
The short answer to which is better: for a buyer choosing a finished stone, neither method is inherently superior. A well-grown, well-cut diamond from either route is an excellent diamond, and once cut and set it is not possible to tell them apart by eye. The growth method is recorded on the grading report and is worth knowing about, but it should not be the primary basis for choosing between two stones.
What should drive the choice is the same thing that drives it with natural diamonds: the four grades, the cut quality in particular, and what the report actually says.
| HPHT | CVD | |
| Full name | High Pressure High Temperature | Chemical Vapour Deposition |
| How it works | Mimics the pressure and heat of natural formation | Carbon is deposited layer by layer from a gas |
| Typical crystal form | Cuboctahedral | Tabular / plate-like |
| Common characteristics | Occasional metallic flux inclusions | Occasional graining or a subtle tint before treatment |
| Post-growth treatment | Less commonly needed | HPHT processing to improve colour is common |
| Is it a real diamond | Yes | Yes |
| Graded on the same scales | Yes | Yes |
Appearance and design differences
In a finished ring, there is no appearance difference attributable to growth method. A G-colour VS1 round brilliant looks like a G-colour VS1 round brilliant regardless of how the crystal was grown. Any visible difference between two stones comes from their grades and their cut, not their production route.
Where the methods differ is in the shape of the rough crystal they produce, and that has a modest downstream effect on what shapes are efficient to cut.
- HPHT rough grows in a cuboctahedral form, similar in general character to natural rough. It lends itself well to round brilliants and to shapes that use a broadly symmetrical crystal.
- CVD rough grows as a flatter, tabular plate. That geometry suits elongated and rectangular shapes efficiently — emerald, radiant and oval among them.
This is a production consideration rather than a buying one. It occasionally means a particular shape is more readily available from one route than the other at a given size, but it does not make the resulting stone better or worse. Choose the shape you want and let availability follow.
Quality and technical differences: laboratory-grown disclosure, grading report, growth method where relevant and value trade-offs
Disclosure. Both HPHT and CVD stones must be disclosed as laboratory-grown. The accepted terms are “laboratory-grown”, “lab-grown” and “laboratory-created”. Language that obscures origin is a reason to ask direct questions and, if the answers are vague, to walk away.
The grading report. Both are graded by the major laboratories on the same 4Cs scales used for natural diamonds, and the report states clearly that the stone is laboratory-grown. Reports for lab-grown stones generally identify the growth method, and stones are usually laser-inscribed with the report number and a note of their laboratory-grown origin.
Growth method, and where it genuinely matters. There are two situations where the method is worth knowing. The first is inclusion type: HPHT stones occasionally contain small metallic flux inclusions left from the growth process, which can in principle respond to a magnet in loose rough and which appear on the plot like any other inclusion. CVD stones more often show graining or striation. Neither is a defect in a stone that grades well; both are simply characteristic.
The second is treatment. CVD material frequently receives post-growth HPHT processing to improve its colour. This is routine, it is permanent, and it is not a fault — but it is a material fact about the stone and it must be disclosed on the report. Ask directly whether a stone has been treated after growth, and expect the answer to be documented rather than verbal.
Value trade-offs. We make no claims about how either growth method holds value. Laboratory-grown diamonds trade in a different market from natural stones, and that market is younger. Anyone weighing resale should treat it as a question for independent advice rather than for a seller. Our page on lab-grown vs natural diamond price covers how the two categories are priced.
Price and value considerations
We do not publish prices, and we do not publish a premium or discount between the two growth methods, because such a figure would move with production capacity and would be out of date quickly.
What is durable is the principle: price follows the grades, not the growth method. Two stones of the same weight, shape and grade combination will be priced similarly whether grown by HPHT or CVD. Where you see a meaningful price difference between two lab-grown stones, look at the specification before assuming the method explains it.
The factors that actually move the figure:
- Cut quality — the grade with the most visible effect and the one worth paying for.
- Colour and clarity — graded identically to natural stones, and priced accordingly.
- Carat weight — with the same step-ups at round weights that apply to natural diamonds.
- Shape — round brilliants cost more per carat than most fancy shapes.
- Post-growth treatment — disclosed on the report, and a legitimate question to ask about price.
- The issuing laboratory — grading standards are not perfectly uniform, so identical letters from different laboratories are not identical stones.
Durability, maintenance or ownership trade-offs
There is no durability difference between the two methods worth acting on. Both produce diamond, which sits at 10 on the Mohs scale — the hardest naturally occurring material, and equally hard whether grown underground or in a reactor.
Diamond is hard but not indestructible. It has cleavage planes and can chip if struck at the wrong angle, and that is true of natural, HPHT and CVD stones alike. The practical protections are the same for all three: a well-made setting, a bezel or protected corners for shapes with vulnerable points, and taking the ring off for genuinely rough work.
Maintenance is identical too. Cleaning, prong checks and periodic professional inspection apply the same way; our guide to cleaning a diamond ring covers the routine. Rhodium re-plating, where relevant, is a function of the metal rather than the stone.
One ownership point specific to lab-grown stones of either method: keep the report. Because origin must be disclosed on resale and to insurers, the documentation matters more than it does for a natural stone of similar grades.
Who each option suits
Framed honestly, this is less a choice between two buyer types than a question of what is available in the specification you want.
| If you | HPHT | CVD |
| Want a round brilliant | Well suited; the rough form lends itself to it | Also widely available |
| Want an elongated or rectangular shape | Available | The rough geometry suits these efficiently |
| Want to avoid post-growth treatment | More often untreated | Ask; HPHT processing after growth is common |
| Are choosing on grades alone | Method is not the deciding factor | Method is not the deciding factor |
| Care about inclusion type | Metallic flux inclusions possible | Graining or striation possible |
In practice, most buyers should specify the shape, the weight and the grade combination they want, then look at what is available across both routes and choose the best-cut stone with the clearest report. That approach produces a better outcome than deciding on growth method first and shopping within it.
A note on how the two methods are often described
It is worth being sceptical of marketing that presents one growth method as a premium product and the other as a lesser one. Both routes are used at every quality level, and both produce stones across the full range of the grading scales.
The useful questions are always about the individual stone: what the report says, whether it has been treated after growth, and how well it is cut. A seller who answers those three questions clearly is giving you what you need. A seller who talks at length about the method while being vague about the report is not.
Which option should you choose?
Choose on the stone, not the method. If two diamonds have the same grades, the same cut quality and clean reports, the growth method is not a reason to prefer one over the other, and any seller telling you otherwise should be asked to explain why in specific terms.
Ask these three questions of any lab-grown stone you are considering, whichever route produced it: which laboratory issued the report and when; whether the stone has received any post-growth treatment; and what the cut grade or, for fancy shapes, the measured proportions are.
If you want a starting point, lab-grown diamonds in South Africa covers the category, what is a lab-grown diamond explains how they are made and graded, and lab-grown diamond rings shows finished pieces. For loose stones, see loose lab-grown diamonds.
Tell us the specification, not the method
Give us the shape, weight and grades you want and we will show you what is available across both growth routes, with the report for each.