CVD vs HPHT: what buyers need to know
Both methods make real diamond. They differ in what they grow best, how stones are treated after growth, and what you should ask the supplier to disclose.
How each is grown
CVD (chemical vapour deposition) grows diamond layer by layer on a thin diamond seed plate, inside a vacuum chamber where a microwave plasma breaks down methane and hydrogen. Growth takes weeks. Growers run hundreds or thousands of reactors at once.
HPHT (high pressure, high temperature) recreates the conditions deep in the earth: carbon dissolved in a metal solvent crystallises onto a diamond seed inside a press at roughly 50,000–60,000 bar and 1,300–1,600 °C.
Side by side
| CVD | HPHT | |
|---|---|---|
| Main growing countries | India leads | China leads |
| Strong in | Larger white stones, Type IIa material | Small sizes (melee), some fancy colours |
| Typical colour story | Often grown slightly brown or grey, then improved with post-growth treatment | Often colourless as grown; blue from boron, yellow from nitrogen |
| Crystal shape | Flat, tabular | Cuboctahedral |
| Is it real diamond? | Yes | Yes |
A buyer looking at a polished stone cannot tell the method by eye. Labs can, and good reports state it.
Treatment
Many CVD diamonds receive an HPHT treatment after growth to remove brown tints. Pink lab-grown diamonds are usually produced by treatment as well. None of this is a problem if it is disclosed. Ask the supplier to state "as grown" or "treated" for every stone, and check that the report agrees.
How to specify
Unless you have a reason to prefer one method, specify the result you need (size, shape, colour, clarity, report) and let suppliers offer either method, stated per stone. If your customers ask for "as grown" or a specific method, put it in the RFQ. Our RFQ template includes both.
Questions
Can you tell CVD from HPHT by eye?
No. The difference shows only in lab testing: growth patterns, fluorescence and spectroscopy. Ask the supplier to state the method and check the lab report.
Are treated lab-grown diamonds worse?
Not necessarily. Post-growth treatment is common, especially for CVD. It should be disclosed on the report and invoice so you can describe the stone correctly to your customers.
From the publisher
Run INTI through the same checks.
INTI Diamonds grows CVD and HPHT lab-grown diamonds in India: white goods, fancy colours and large stones. Ask us for anything on the checklist, including a live video call of the factory before you pay.
We publish this guide. We would rather win your order by passing the checks than by hiding them.