HPHT and CVD are the two main ways of growing a diamond in a laboratory: HPHT recreates the intense pressure and heat found deep in the earth, while CVD builds a diamond up layer by layer from a carbon rich gas. Both methods produce real diamond with the same chemistry and hardness, so for most people the quality of the individual stone matters far more than how it was grown.
The two names come up a lot on grading reports and product listings, so it helps to know what they mean and when the difference is worth thinking about.
What is HPHT?
HPHT stands for high pressure, high temperature. A small diamond seed is placed in a press with a source of carbon and a metal solvent, then subjected to enormous pressure and heat. The carbon dissolves and crystallises onto the seed, and the diamond grows over a period of days or weeks.
Because a metal solvent is used, some HPHT diamonds contain small metallic inclusions. These are usually only visible under magnification, and a well chosen stone can be very clean.
What is CVD?
CVD stands for chemical vapour deposition. Thin diamond seed plates are placed in a vacuum chamber filled with a carbon rich gas, which is heated until it breaks down. Carbon atoms settle on the seeds and the diamond grows in layers.
Many CVD diamonds are given a further heat and pressure treatment after growth to improve their colour. GIA reports that most CVD stones receive this kind of post-growth treatment. It is a recognised and stable step, and grading reports note it.
Illustration of an oval solitaire, not a finished À Vie piece.
HPHT vs CVD at a glance
| HPHT | CVD | |
|---|---|---|
| How it grows | Carbon crystallises under heat and pressure | Carbon settles from a gas in layers |
| Typical inclusions | Can include tiny metallic traces | Can show fine graining or dark specks of carbon |
| After growth | Often sold as grown | Often treated to improve colour |
| Is it real diamond? | Yes | Yes |
Does the growth method affect how a diamond looks?
Not in any way you would notice on the hand. Once a diamond is cut and polished, its sparkle comes from the cut, and its appearance depends on its colour and clarity grades. Two stones with the same grades, one HPHT and one CVD, can look identical.
Where the method can show up is in the detail. Some HPHT stones are weakly magnetic because of metallic inclusions, and some CVD stones show faint strain under specialist lighting. These are things a gemmologist looks for, not things you see when you wear the ring.
Is one better than the other?
Neither method is better in itself. Both can produce excellent diamonds, and both can produce poor ones. Rather than choosing by method, we suggest judging each stone on its grading report and on how it looks:
- Cut grade, which has the biggest effect on sparkle.
- Colour and clarity, checked against the report.
- Any treatment noted on the report, so you know exactly what you are buying.
Lab-grown diamonds we work with come with GIA or IGI reports, which state that the stone is laboratory grown. Our guide to GIA vs IGI reports explains how to read them.
Can you tell if a diamond is HPHT or CVD?
Not by eye. Grading laboratories use specialist equipment to identify how a diamond was grown, and many reports record the method. If it matters to you, ask to see the report before you commit to a stone.
Natural treatments are a different topic
HPHT is also the name of a treatment applied to some natural diamonds to change their colour. That is separate from growing a diamond from scratch. Our article on diamond treatments covers it.
Choosing a lab-grown diamond with us
We can talk you through the report for any lab-grown stone we suggest, including the growth method and any treatment noted, before you commit. Your design starts as a CAD render with revisions within reason, and a 70% deposit starts the making once you approve it. Your ring is crafted by specialist goldsmiths, UK hallmarked and sent by insured tracked courier. Bespoke rings start from £600.
Browse our lab-grown colourless diamonds or read about the bespoke journey to see how a commission works.
Frequently asked questions
Are HPHT and CVD diamonds real diamonds?
Yes. Both methods grow real diamond, with the same chemical make up and hardness as a mined diamond.
Which is better, HPHT or CVD?
Neither method is better in itself. Judge each stone on its cut, colour and clarity grades and on how it looks.
Can you see the difference between HPHT and CVD diamonds?
Not by eye. A grading laboratory uses specialist equipment to identify the growth method.
Does the grading report say how a lab-grown diamond was made?
GIA and IGI reports state the growth process and evidence of post-growth treatment. Ask to see the report before you choose a stone.