CVD vs HPHT Lab Grown Diamonds: What's the Difference?
If you shop for lab grown diamonds you will soon see two abbreviations: CVD and HPHT. They are the two ways lab grown diamonds are made. Both produce real diamonds with the same properties as mined ones. Here is how each works and whether the difference should matter to you.
HPHT: high pressure, high temperature
HPHT recreates the conditions deep inside the earth where natural diamonds form. A small diamond seed is placed in a press with a carbon source and a molten metal that helps the carbon dissolve. The press applies roughly 50,000 times normal air pressure at temperatures of around 1,300 to 1,600 °C, and the carbon crystallizes onto the seed as diamond.
- HPHT crystals tend to grow in a cuboctahedral shape, with growth in several directions at once.
- Tiny traces of the metal used in growth can sometimes remain as inclusions.
- HPHT can produce very white, high-color stones.
CVD: chemical vapor deposition
CVD grows diamond from a gas. Thin, flat diamond seed plates are placed in a vacuum chamber filled with a carbon-rich gas, usually methane mixed with hydrogen. Energy, often from microwaves, turns the gas into a plasma, and carbon atoms settle onto the seeds, building diamond up layer by layer at far lower pressure than HPHT.
- CVD crystals grow in flat, tabular layers.
- Some CVD diamonds come out of the chamber with a slight brown tint, so many are given a post-growth HPHT treatment to improve their color. This treatment is permanent.
- CVD allows many stones to be grown at once and is widely used for larger diamonds.
Side by side
| HPHT | CVD | |
|---|---|---|
| How it grows | Carbon crystallizes in a high-pressure press | Carbon deposits from a gas plasma, layer by layer |
| Conditions | Very high pressure and temperature | Low pressure, high temperature |
| Crystal shape | Cuboctahedral | Flat, tabular |
| Typical traits | Possible tiny metallic inclusions | Possible strain patterns; often color-treated after growth |
| Result | Real diamond | Real diamond |
Does the method matter?
For beauty and durability, not much. A finished, polished diamond is judged by its cut, color, clarity and carat, not by how it was grown. Both methods can produce excellent stones and both can produce poor ones. Two diamonds with the same grades will look the same to the eye, whichever way they were made.
What matters more:
- Cut quality, which drives sparkle.
- Color and clarity that look clean and white to your eye.
- Size in millimetres for the shape you love.
- A secure setting in solid gold or platinum.
Can you tell CVD from HPHT by eye?
No. Telling the two apart, or telling a lab grown diamond from a mined one, needs specialized laboratory equipment. Independent grading reports often state the growth method and whether the stone was treated after growth.
At Bhumi Gems
Our lab grown diamond listings describe the centre stones as E-F color and VVS clarity, and each piece ships with a Bhumi Gems certificate of authenticity. If you would like to know the growth method for a specific stone, ask us before you order. Learn more in our lab grown diamonds guide and are lab grown diamonds worth it?
Quick answers
Is CVD or HPHT better?
Neither is better in itself. Judge each stone by its grades and how it looks.
Are CVD and HPHT diamonds real diamonds?
Yes. Both are carbon crystals with the same properties as mined diamonds.
Is post-growth treatment a problem?
Post-growth HPHT treatment used to improve the color of CVD diamonds is permanent. It should be disclosed, and independent reports note it.
Ready to look? Browse our lab grown diamond engagement rings.