HPHT laboratory-grown diamonds
HPHT lab-grown diamonds, cut and polished in India
HPHT laboratory-grown diamonds, cut and polished on our own line and supplied direct to the trade.
What HPHT means
HPHT (high pressure, high temperature) recreates the conditions deep in the earth where natural diamonds form. A small diamond seed sits in a cell with a carbon source and a molten metal solvent. Large presses squeeze the cell to roughly 50,000–60,000 bar and heat it to around 1,300–1,600 °C. Carbon dissolves in the metal and crystallises on the seed.
HPHT rough grows as a cubo-octahedral crystal. It is well suited to bright colourless stones, to melee and smaller sizes, and to colours that come from trace elements: yellow from nitrogen and blue from boron.
What HPHT stones can show
- Metallic inclusions. Tiny traces of the metal solvent can remain. Grading reports describe them like any other inclusion.
- Colour zoning. Growth sectors can take up nitrogen or boron differently, which matters in fancy colours.
- Phosphorescence. Some HPHT diamonds glow briefly after strong UV light. It is a recognised identification feature, not a defect.
CVD or HPHT?
| CVD | HPHT | |
|---|---|---|
| How it grows | Carbon from a methane–hydrogen plasma settles on flat diamond seed plates, layer by layer | Carbon dissolves in molten metal under about 50,000–60,000 bar and grows on a seed crystal |
| Crystal habit | Tabular (flat) rough | Cubo-octahedral rough |
| Diamond type | Usually Type IIa (no measurable nitrogen) | Type IIa for colourless; Type Ib (yellow) or IIb (blue) when nitrogen or boron is present |
| Often used for | Larger white stones, pinks | Strong colourless whites, blues, yellows, melee |
| Post-growth treatment | Common, to improve colour; must be disclosed | Less common for colourless; used for some fancy colours |
| Report states method | Yes | Yes |
What to specify
| What to specify | Typical options |
|---|---|
| Shape | Round brilliant, oval, emerald, cushion, pear, radiant, princess, marquise, asscher, heart |
| Size | Single stones by carat, or calibrated parcels by millimetre |
| Colour | D–F, G–H, I–J for white; fancy colours by hue and intensity |
| Clarity | IF, VVS1–VVS2, VS1–VS2, SI1–SI2 |
| Cut, polish, symmetry | Excellent / Very Good for rounds; proportions to your brief for fancy shapes |
| Report | IGI, GIA or another laboratory, or ungraded parcels |
| Growth and treatment | As-grown or post-growth treated, always disclosed |
Send us your requirement
Use the requirement form or email [email protected] with:
- Shape: round, oval, emerald, cushion, pear, radiant, princess, marquise, asscher, heart or others
- Carat range per stone, or total carats for a parcel
- Colour and clarity range
- Quantity, and whether you need matched pairs or calibrated sizes
- Grading reports, if you need them, and which laboratory
- Delivery country and the date you need the goods
We reply with what we have in stock and what we can grow for you.
Questions buyers ask
What is the difference between CVD and HPHT diamonds?
Both make real diamond. CVD grows diamond from a carbon-rich plasma onto flat seed plates; HPHT grows it in molten metal under very high pressure and temperature. Polished stones from either method are graded on the same scales, and the grading report states which method was used.
Which grading laboratories do you work with?
We can supply stones with reports from IGI, GIA or another laboratory you prefer, or as ungraded parcels for melee and calibrated goods. Tell us your requirement when you enquire.
Can you make matched pairs and calibrated parcels?
Yes. Tell us the shape, size tolerance and quantity, and we will quote from stock or plan a production run.
Do you supply fancy colours?
Yes, we work in fancy colours including pink, blue and yellow. Ask us what is available now and what we can grow to order.