CVD vs HPHT: Does the Growth Method Matter to a Buyer?

Lab Grown Diamonds

Mostly no — and knowing why is more useful than knowing which.

Written by the Mapple Gems workshop, Surat · Updated 26 August 2026

Short answer

Both produce real diamond. HPHT recreates the pressure and temperature of the earth’s mantle; CVD grows a crystal layer by layer from carbon-rich gas. Once cut and polished, a finished stone of a given colour and clarity is a finished stone — the method is not a quality ranking, and neither is inherently better. It appears on your grading report because it is a fact about origin, not a warning. Buy on the 4Cs and the report, not on the acronym.

This question comes up because the growth method is printed on grading reports, and anything printed on a report looks like it must matter. It is worth understanding, but it should not drive your decision, and sellers who present one method as superior are usually describing their own supply chain rather than your interests.

What each method actually does

HPHT — High Pressure, High Temperature. The older approach. A small diamond seed, carbon source and metal catalyst are subjected to extreme pressure and temperature, reproducing the conditions under which diamonds form naturally. The crystal grows outward in a cuboctahedral shape.

CVD — Chemical Vapour Deposition. A seed plate sits in a chamber filled with carbon-rich gas, typically methane and hydrogen. The gas is energised into a plasma, and carbon atoms deposit onto the seed layer by layer. The crystal grows as a flat tablet rather than a cube.

Different routes, same destination: crystalline carbon in the diamond lattice.

	HPHT	CVD
Crystal shape	Cuboctahedral	Flat tablet
Typical inclusions	Metallic flux traces	Non-metallic, graphitic
Post-growth treatment	Less commonly needed	Often HPHT-treated to improve colour
Scaling to large sizes	Harder	Easier — most large stones are CVD
Visible difference once cut	None	None

The claim to be sceptical of. You will find sellers arguing that one method produces “purer” or “more brilliant” diamonds. Both claims fail the same test: a graded stone has already been assessed for colour and clarity by an independent laboratory. If a CVD stone and an HPHT stone are both, say, F colour and VS1, then they are both F colour and VS1 — that is what the grading was for. A method preference cannot outrank a measurement. When you see this argument, it almost always maps onto what that seller happens to source.

The one thing worth knowing: post-growth treatment

This is the genuinely useful part of the CVD/HPHT distinction, and it is about treatment rather than growth.

CVD stones sometimes emerge with a brownish tint, which can be removed by an HPHT treatment after growth. This is standard, permanent and disclosed on grading reports — you may see wording indicating the stone has been treated or is “as grown”.

Is treatment a problem? Not for durability or appearance — it is permanent and the stone will not revert. But it is a fact you are entitled to know, and it is one of the things a proper laboratory report tells you that a seller’s own card does not.

“As grown” stones, needing no treatment, sometimes carry a small premium. Whether that is worth paying is a preference, not a quality difference you will see.

Why most large stones are CVD

Worth knowing if you are shopping above about 2 ct. CVD scales to larger crystals more readily than HPHT, so the large-stone market skews heavily CVD.

This is why some buyers form the impression that CVD is “for big stones” and HPHT “for small ones”. It is a production economics fact, not a quality signal — and it means that at larger sizes you may simply have less choice of method regardless of any preference.

What you should actually buy on

Cut, first. It is the only factor that changes how the stone looks in ordinary light, and for round brilliants it is graded.
Eye-clean clarity, not the highest grade — unless it is a step cut, where clarity matters more.
Colour matched to your setting metal, not to the top of the scale.
An IGI or GCAL report with full 4C detail — noting that since October 2025, GIA issues a Premium or Standard assessment for lab grown rather than letter grades.
The price against the current market, never against a struck-through “compare at” figure.

Growth method does not appear on that list, and that is deliberate.

Keep reading

Frequently asked questions

Is CVD or HPHT better for lab grown diamonds?

Neither is better. Both produce real diamond, and once cut and polished there is no visible difference. A stone graded at a given colour and clarity is that colour and clarity regardless of how it was grown, so buy on the 4Cs and the report rather than on the growth method.

What is the difference between CVD and HPHT?

HPHT recreates the extreme pressure and temperature of the earth’s mantle around a diamond seed, growing a cuboctahedral crystal. CVD deposits carbon from an energised gas onto a seed plate layer by layer, growing a flat tablet. They differ in typical inclusion types and how easily they scale to larger sizes.

Are CVD diamonds treated after growth?

Often, yes. CVD stones can emerge with a brownish tint that an HPHT treatment removes. The treatment is permanent, does not affect durability, and is disclosed on independent grading reports. Untreated “as grown” stones sometimes carry a small premium, which is a preference rather than a visible quality difference.

Why are most large lab grown diamonds CVD?

Because CVD scales to larger crystals more readily than HPHT does, so the large-stone market skews heavily toward it. This is production economics rather than a quality signal — but it does mean that above roughly 2 ct you may have less choice of growth method whatever your preference.

We will tell you the method — and why it should not decide your purchase.

Every lab grown centre stone comes with an IGI report showing growth method and full 4C detail.

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