What Is a Lab-Grown Diamond: direct answer
A laboratory-grown diamond is a diamond. Same carbon crystal structure, same hardness, same refractive index, same optical behaviour, graded on the same scales by the same laboratories as a mined stone. It is not a simulant and it is not an imitation.
The only difference is where it came from. A mined diamond crystallised in the earth’s mantle over geological time; a laboratory-grown diamond was grown in a reactor over a period of weeks, from a small seed crystal.
Because they are the same material, the practical questions are not about quality — they are about disclosure, price and what the origin means to you. This page covers how they are made, how they are graded and identified, and what to check before buying one.
What this term or grading factor means
Two production methods dominate, and both produce genuine diamond.
- HPHT (High Pressure High Temperature) reproduces conditions similar to those in the earth’s mantle, applying high pressure and temperature to carbon around a seed crystal. It is the older of the two methods and is also used to treat diamonds after growth.
- CVD (Chemical Vapour Deposition) grows the crystal layer by layer from a carbon-rich gas inside a vacuum chamber, at lower pressure. It has become the more common method for gem-quality material.
- Post-growth treatment. Some laboratory-grown stones are treated after growth to improve their colour. This is legitimate and common, but it should be recorded on the grading report, and treated and untreated stones are not priced alike.
How it is assessed or identified: laboratory-grown disclosure, grading report, growth method where relevant and value trade-offs
Grading and identification both work slightly differently from mined stones, and it is worth knowing how.
Disclosure is not optional
Laboratory-grown origin must be disclosed clearly and in writing, on the grading report and at the point of sale. Vague language is the warning sign to act on — wording that blurs the line between grown and mined, or between diamond and simulant, should prompt you to ask for the report and read the origin line yourself.
A reputable seller states origin without being asked. If you have to work for the answer, that is itself informative.
How they are graded
Laboratory-grown diamonds are assessed on cut, colour, clarity and carat using the scales set out in GIA’s grading methodology. Report formats for laboratory-grown stones differ from those issued for mined diamonds, and the range of report types is described in GIA’s guide to report types.
The practical implication when comparing two stones is to check they come from the same laboratory and the same report type. An abbreviated report covers less ground than a full one, so the grades are not directly comparable across formats.
How they are identified
This is where most confusion lives. You cannot tell a laboratory-grown diamond from a mined one by eye, and neither can a jeweller without instruments — there is nothing visual to distinguish. The handheld testers sold as diamond testers measure conductivity, and a laboratory-grown diamond is diamond, so it registers as diamond. That is the instrument working correctly.
Separating origin requires spectroscopy and imaging available to gemmological laboratories, which examine growth structures and trace characteristics that differ between mantle-formed and reactor-grown crystals. That is why the grading report is the proof of origin rather than any counter test.
What buyers should look for
Five checks, in order.
- Confirm the report states laboratory-grown origin explicitly, in writing.
- Verify the report number on the issuing laboratory’s own database rather than trusting a printed sheet, and check the measurements and any girdle inscription against the stone.
- Check the treatment line. Ask directly whether the stone was treated after growth to improve colour.
- Note the laboratory and report type, since both affect comparability and price.
- Protect the cut grade. Because these stones cost less per carat, the temptation is to buy size and accept weaker proportions. That is the one trade that reliably disappoints, and it is worth resisting deliberately.
How it affects appearance, quality or price
Laboratory-grown diamonds cost substantially less per carat than mined stones of equivalent grade, and that gap widens as carat weight increases. What that buys most buyers is a larger stone, stronger grades, or both. Three things deserve to be stated plainly rather than glossed over. Prices have fallen considerably as production capacity expanded and remain less stable than mined pricing, so any figure should be treated as current at its date. The secondary market is limited and not comparable to that for mined stones. And neither should be bought as an investment — jewellery is not a regulated investment product and we do not provide investment or financial advice. None of that argues against buying one; it argues for buying it as jewellery, which is the sound basis either way.
How long they take to grow, and why that matters less than you would think
A gem-quality laboratory-grown diamond takes a matter of weeks to grow rather than the geological timescales involved in a mined stone. That contrast is the fact most often quoted about them, and it is genuinely striking — but it tells you nothing about the finished stone.
A diamond grown in three weeks and one formed over an immense span of time are the same material with the same crystal structure and the same hardness. The growth time affects the economics of production, not the properties of the result. Where it does matter to a buyer is indirectly: because production can be scaled and repeated, supply responds to demand in a way mined supply cannot, which is why prices have moved.
Are they the same as a diamond simulant
No, and this is the most consequential confusion in the subject. A simulant — cubic zirconia, moissanite, white sapphire — is a different material chosen because it resembles diamond. It has different hardness, different optical properties, and it is not graded on the diamond scales.
A laboratory-grown diamond is diamond. If you put one in front of a gemmologist without its paperwork, they would need specialist instruments to distinguish it from a mined stone, because there is essentially nothing else to go on. A simulant, by contrast, can be separated with a basic tester in seconds. The two sit on opposite sides of a real line, and conflating them leads buyers to dismiss laboratory-grown diamonds for reasons that simply do not apply to them.
Common misunderstandings and mistakes
- “Lab-grown diamonds are fake.” They are diamond. The distinction is origin, not authenticity.
- “They are the same as cubic zirconia or moissanite.” They are not. Those are simulants — different materials with different hardness and optical properties. A laboratory-grown diamond is diamond.
- “They will cloud or wear out.” They will not. Same hardness as any diamond, and no different in wear.
- “A diamond tester can tell the difference.” It cannot. It measures conductivity, and a laboratory-grown diamond passes because it is diamond.
- “The growth method matters a lot.” For most buyers it does not. What matters is the finished stone’s grades and whether it was treated after growth.
- “They hold their value like mined stones.” They do not, and no honest seller will say otherwise.
What to do next before buying
Decide the origin question first, since it changes every other decision. Continue at lab-grown vs natural diamond to weigh it properly, at lab-grown diamond rings South Africa to see finished rings, or at diamond certificate explained to learn how to read a report. For the whole process, the diamond buying guide.
Continue to the relevant buying guide or book expert guidance
Tell us the size, shape and budget you have in mind and we will show laboratory-grown options with full grading reports stating origin and treatment — and, if it helps, a comparable mined stone alongside, so you can see for yourself that at equal grades they are indistinguishable.