CVD and HPHT Lab-Grown Diamonds: What They Mean on Your Report

CVD (chemical vapour deposition) and HPHT (high pressure, high temperature) are the two main ways diamonds are grown in a laboratory. CVD builds the crystal layer by layer from a carbon-rich gas, while HPHT recreates intense pressure and heat around a small diamond seed. Both produce real diamond, and the grading report for a lab-grown diamond states clearly that it is laboratory-grown and often notes the growth method and any treatment after growth.

What is a CVD lab-grown diamond?

In the CVD method, a thin slice of diamond, called a seed, is placed in a sealed chamber. A gas containing carbon, usually methane mixed with hydrogen, is heated until it breaks down. Carbon atoms then settle on the seed and build up the diamond crystal one layer at a time.

The process takes several weeks. The rough crystal is then cut and polished like any other diamond. Some CVD diamonds receive a further treatment after growth to improve their colour; a good report records this.

What is an HPHT lab-grown diamond?

In the HPHT method, a small diamond seed is placed with a carbon source and a metal mixture inside a press. The press creates very high pressure and temperature, the carbon dissolves and then crystallises on the seed, growing a new diamond.

HPHT crystals often grow in a different shape from CVD crystals, but once cut and polished they are graded on the same scales of cut, colour, clarity and carat.

Are CVD and HPHT diamonds real diamonds?

Yes. Both methods produce a crystal of carbon with the same structure, hardness and optical properties as diamond. That is why a lab-grown diamond tests as diamond on a standard tester. What a tester cannot show is how the diamond was formed; for that, you rely on the grading report and the laser inscription.

You can read more on our lab-grown diamond jewellery page.

Is the growth method written on the grading report?

Grading reports for lab-grown diamonds state that the diamond is laboratory-grown. Many reports also note the growth method (CVD or HPHT) and mention any post-growth treatment in the comments section. The exact wording depends on the laboratory.

When you read your report, look for:

The origin statement: that the diamond is laboratory-grown.
Growth method: CVD or HPHT, if listed.
Comments: any note on post-growth treatment.
The report number: which should match the number laser-inscribed on the girdle of the stone.
The 4Cs: carat weight, colour, clarity and cut, plus measurements and shape.

Our guide on how to read an IGI certificate for lab-grown diamond jewellery goes through a report line by line.

How can I verify my lab-grown diamond myself?

At Vaishnavi Jewels, every solitaire comes with its own grading report from IGI, EGL or TGL, and its report number is laser-inscribed on the stone. You can:

Look at the girdle under a 10x loupe to read the inscription.
Check that it matches the number on your report.
Enter the number on the laboratory’s website to see the online record.

Every jewellery piece also comes with a jewellery grading report, small diamonds are described by total weight, number of pieces and quality, and the gold carries a BIS HUID hallmark you can check in the BIS Care app. We do these checks with you at the counter before you pay.

Does the method affect how the jewellery is made or worn?

No. Once cut, a lab-grown diamond is set, worn and cared for just like any diamond. We make lab-grown diamond jewellery in our own manufacturing unit, so you can choose the design, gold karat and diamond quality, made to suit your budget. Custom pieces usually take 2 to 4 weeks depending on the design.

Should I choose a stone by its growth method?

For most buyers, the growth method is a detail to understand rather than a deciding factor. What you see and wear is the cut, colour, clarity and carat of the finished stone, and those are graded on the report in the same way whichever method was used. Read the report, look at the stone under a loupe, and choose the diamond whose size, shape and look you like best. We are happy to show you several lab-grown stones side by side with their reports so you can decide in person.

Frequently asked questions

Do lab-grown diamonds pass a diamond tester?

Yes, they test as diamond because they are diamond. A tester cannot show how a diamond was formed; the grading report and the matching laser inscription confirm that.

Does a lab-grown diamond come with an IGI certificate and a laser inscription?

At Vaishnavi Jewels, every lab-grown solitaire comes with a grading report from IGI, EGL or TGL stating that it is laboratory-grown, and the report number is laser-inscribed on the stone so you can verify it online.

How do I verify an IGI diamond report online?

Read the report number laser-inscribed on the stone under a loupe, then enter it on the laboratory’s website and check that the details match your report. We can do this with you in the showroom.

Ask us to walk you through a lab-grown diamond report at our Parle Point showroom, visit our showroom, or WhatsApp +91 99980 43886.