What a lab-grown diamond is
A lab-grown diamond is a diamond. It is carbon, crystallised in the same cubic structure as a diamond formed in the earth, with the same hardness, the same refractive index and the same fire. The only difference is its origin. It grew in a laboratory over a few weeks, not underground over one to three billion years.
It is also called a laboratory-grown, lab-created or man-made diamond. It is not a simulant. Cubic zirconia and moissanite are different materials that imitate diamond. A lab-grown diamond is the material itself.
- Material
- Carbon
- Hardness
- 10 on the Mohs scale
- Refractive index
- 2.42
- Time to grow
- A few weeks
- Methods
- HPHT and CVD
- Graded on
- Cut, colour, clarity, carat
How a diamond is grown
There are two methods. Both begin with a seed, a small piece of existing diamond, and both end with a rough crystal that is cut and polished exactly as a mined diamond is.
HPHT
High Pressure High Temperature copies the conditions deep in the earth. The seed is placed in a press with carbon and a metal catalyst. At around 1,300 to 1,600 degrees Celsius and more than 50,000 atmospheres, the carbon dissolves and crystallises on the seed. General Electric announced the first repeatable process in 1955.
CVD
Chemical Vapour Deposition builds a diamond from gas. A thin slice of diamond is placed in a vacuum chamber filled with a carbon-rich gas, usually methane with hydrogen. Microwaves turn the gas into plasma at around 800 to 1,200 degrees Celsius. Carbon atoms settle on the seed and the crystal grows upward, layer by layer.
Some CVD diamonds are treated with heat and pressure after growth to improve their colour. A grading report states this when it applies.
Both methods produce real diamond, and neither is better in itself. What matters is the quality of the finished stone, and that is what a grading report measures.
Lab-grown, mined and simulants compared
The first two columns below are the same material. The last two only look like it.
| Property | Lab-grown diamond | Mined diamond | Moissanite | Cubic zirconia |
|---|---|---|---|---|
| Material | Carbon | Carbon | Silicon carbide | Zirconium dioxide |
| Is it diamond | Yes | Yes | No | No |
| Hardness, Mohs | 10 | 10 | 9.25 | 8 to 8.5 |
| Refractive index | 2.42 | 2.42 | 2.65 to 2.69 | 2.15 to 2.18 |
| Origin | Grown in a laboratory in weeks | Formed in the earth over 1 to 3 billion years | Made in a laboratory | Made in a laboratory |
| Graded on the four Cs | Yes | Yes | No | No |
Because a lab-grown diamond and a mined diamond are the same material, no jeweler can tell them apart by eye or with a loupe. A gemmological laboratory can, using instruments that read growth patterns and trace elements.
Two of these comparisons have a guide of their own: lab-grown and natural diamonds, and lab-grown diamond or moissanite.
How lab-grown diamonds are graded
An independent laboratory examines the diamond and issues a report. The report records the four Cs, the measurements and proportions of the stone, and the fact that it is laboratory-grown.
- IGI, the International Gemological Institute, grades lab-grown diamonds on the same cut, colour and clarity scales used for mined diamonds. Its reports are the ones most often seen with lab-grown stones.
- GIA, the Gemological Institute of America, changed its approach in late 2025. It now describes lab-grown diamonds as premium or standard instead of giving colour and clarity letter grades.
The report number is usually inscribed by laser on the girdle, the thin edge of the diamond, together with words that identify the stone as laboratory-grown. The inscription is invisible to the eye and easy to read under magnification, so a stone can always be matched to its report.
The grades themselves are explained in the four Cs.
Price and value
A lab-grown diamond costs considerably less than a mined diamond of the same grade. It does not carry the cost of mining, and it can be grown to meet demand. Most people use the difference in one of two ways: a larger stone, or a better cut one.
Be clear about resale. Most diamonds, mined or lab-grown, resell for less than their retail price, and lab-grown diamonds currently resell for less than mined ones. A diamond is something to wear. Its value is what you get for the price on the day you buy it.
Mining and energy
A lab-grown diamond is not dug out of the ground. There is no mine and no moved earth, and its origin is known from the first day.
Growing a diamond does take a great deal of electricity, so its footprint depends on the energy the grower uses. We would rather say that plainly than call any diamond green.
What to check before you buy
- Ask for the report. A centre stone should come with a grading report from an independent laboratory.
- Match the inscription. The number on the girdle should be the number on the report.
- Put cut first. Cut decides how bright the diamond is. Colour and clarity matter less than most people expect.
- Look at stones side by side. Two diamonds with the same grades can look different. Compare them in daylight if you can.
- Buy it to wear it. Choose the stone you want to look at every day.
Every piece ART makes is set with lab-grown diamonds. See the collection, or commission a piece.
