How Are Lab-Grown Diamonds Made? CVD vs HPHT Explained
Lab-grown diamonds are made using two main methods: Chemical Vapour Deposition (CVD) and High Pressure High Temperature (HPHT). Both produce genuine diamonds — but they work differently, and understanding the distinction helps you make a more informed purchase.
What Both Methods Have in Common
Regardless of which process is used, all lab-grown diamonds start with a diamond seed — a tiny sliver of existing diamond crystal. The seed acts as a template, and new diamond material grows on top of it, atom by atom, until a full gem-sized crystal is formed. The process takes anywhere from two to twelve weeks depending on the target size and method.
CVD: Chemical Vapour Deposition
CVD is the more common method used for gem-quality lab-grown diamonds today. The diamond seed is placed inside a sealed vacuum chamber, which is then filled with carbon-rich gases — typically methane and hydrogen. The chamber is heated to around 900–1,200°C, and the gases are energised using microwaves or lasers, breaking them apart and releasing carbon atoms.
Those free carbon atoms rain down onto the diamond seed and bond to it in the same crystal structure as the original diamond. Over weeks, a diamond crystal grows layer by layer. The result is a flat, square-ish crystal that's then cut and polished into a finished gem.
CVD diamonds often have fewer metallic inclusions than HPHT diamonds, making them particularly popular for high-clarity stones.
HPHT: High Pressure High Temperature
HPHT mimics the natural conditions deep within the Earth — extreme heat (around 1,500°C) and extreme pressure (around 1.5 million PSI). A diamond seed is placed inside a growth cell with a carbon source (usually graphite) and a metallic catalyst. The combination of heat and pressure causes the carbon to dissolve in the metal and then crystallise around the seed as diamond.
HPHT was the original method for growing diamonds in laboratories, developed in the 1950s. It produces crystals with a different shape than CVD — typically octahedral or cuboctahedral. HPHT is also used to improve the colour of some diamonds after growth.
Which Method Is Better?
Neither method is definitively superior — both produce certified, gem-quality diamonds. The differences come down to subtle characteristics that can affect clarity and colour, which is why both CVD and HPHT diamonds are graded individually by laboratories like IGI.
What matters most is the specific stone's grade, not the method used to grow it. A well-cut, high-clarity CVD stone and a well-cut, high-clarity HPHT stone are both excellent choices for an engagement ring.
Explore our lab-grown diamond solitaire rings — each set with an IGI-certified stone in solid 18K gold or platinum.
Further reading
- The full science behind lab-grown diamonds: CVD and HPHT in depth
- Are lab-grown diamonds real diamonds?
- Cost comparison: lab-grown vs mined diamonds
See Lab-Grown Diamonds at Una Diamond
Every Una Diamond uses IGI-certified lab-grown diamonds — the same technology described above, with full certification: