What Is CVD (Chemical Vapour Deposition)?
CVD diamonds are grown in a vacuum chamber filled with a carbon-rich gas mixture (typically methane). A diamond seed crystal is placed inside the chamber, and microwave energy breaks down the gas molecules, causing carbon atoms to fall onto the seed and crystallise layer by layer over 4–8 weeks. This process produces diamonds with exceptional purity — Type IIa, the same classification as the rarest mined diamonds on earth.
CVD typically produces D–F colourless diamonds with VS+ clarity. The slow, controlled growth allows for tight quality management, making CVD the preferred method for producing consistently high-colour, high-clarity stones. Our Lumina Solitaire, Aurora Halo, Éclat Double Halo, Trilogie Three-Stone, and Belle Époque Vintage are all set with CVD diamonds.
What Is HPHT (High Pressure High Temperature)?
HPHT replicates the conditions deep within the Earth’s mantle, where natural diamonds form. A diamond seed is placed in a growth cell alongside a carbon source and metal catalyst, then subjected to approximately 1,500°C and 1.5 million PSI of pressure. Carbon dissolves into the molten metal and migrates to the cooler seed crystal, building up layer by layer over 2–4 weeks.
HPHT produces diamonds with excellent colour (often D–F) and natural-looking inclusions. The cubic press geometry creates an octahedral crystal structure — identical to mined diamonds. Our Rosée Pavé, Pureté Emerald, and Éternité Full Pavé use HPHT stones.
| Property | CVD | HPHT |
|---|---|---|
| Growth method | Gas chamber, layer by layer | Extreme pressure & heat |
| Colour range | D–F (colourless) | D–F (colourless) |
| Clarity | VS1–VS2 typical | VS1–SI1 typical |
| Price | Slightly higher | Slightly lower |
| GIA certification | Yes — identical to mined | Yes — identical to mined |
| Best for | Round, oval, pear shapes | Emerald, cushion, full pavé |
Which Should You Choose?
In practical terms, CVD and HPHT diamonds are indistinguishable to the naked eye, to standard gemological instruments, and even to most jewellers. The GIA certifies both identically. Choose CVD if you want the absolute highest colour and clarity grades, or HPHT if you prefer a slightly more affordable stone at the same visual quality level.
At Grown Lab Diamond, our gemmologists select the best stone for each ring design — we use CVD where its Type IIa purity shines brightest, and HPHT where its growth geometry best suits the cut. All stones are GIA or IGI certified.
Can a jeweller tell CVD from HPHT?
No standard jewellery instrument can distinguish them. Only specialist laboratory equipment that detects specific growth patterns (like a DiamondView machine) can tell CVD from HPHT — and neither is better or worse in any quality respect.
Do CVD diamonds look different from HPHT?
No. Both methods produce colourless, brilliant diamonds. The differences are in the growth process and crystal structure, not in appearance, durability, or optical performance.
Which has better resale value?
Lab-grown diamonds of both types have a similar resale market. The GIA certificate is what matters most to resellers — whether the stone is CVD or HPHT is secondary.