How lab-grown diamonds are made
Two methods, the same result: a real diamond.
By the CTJ Jewellery team, led by founder Greg Ward · Updated September 2026 · Editorial policy
Key facts
- Two methods: CVD and HPHT
- Both start from a small diamond seed
- Growth takes a few weeks
- Rough is cut and polished like natural
- Graded by IGI or GIA, origin stated
- Girdle inscription identifies it as laboratory-grown
What is CVD?
Chemical vapour deposition. A thin diamond seed plate sits in a vacuum chamber filled with carbon-rich gas. Energy breaks the gas apart, and carbon atoms settle on the seed, building diamond layer by layer.
What is HPHT?
High pressure, high temperature. A diamond seed is placed with a carbon source in a press that recreates the heat and pressure of the earth’s mantle, and the carbon crystallises onto the seed.
CVD or HPHT: which is better?
Neither method is better on its own. Quality depends on the individual diamond, which is why we judge every stone on its grading report and, above all, how it looks.
| CVD | HPHT | |
|---|---|---|
| Process | Carbon from gas, layer by layer | Heat and pressure in a press |
| Typical crystal | Flat, square plates | Cuboctahedral |
| Result | A real diamond | A real diamond |
Is growing diamonds better for the environment?
Lab-grown diamonds avoid mining, but growing them takes a great deal of energy. The footprint depends on how the grower’s power is generated, so it’s worth asking about each diamond.
Ethics and origin