Collectors
- A lab-grown diamond is chemically and optically identical to a mined diamond. It is not moissanite and not cubic zirconia - those are different materials entirely.
- Two growth methods dominate: HPHT, which recreates the pressure and heat of the mantle, and CVD, which builds a crystal layer by layer from carbon-rich gas.
- Grading has moved: IGI still issues full colour and clarity grades, but since October 2025 GIA reports for lab-grown stones use broad Premium and Standard categories instead. Check which system your certificate uses.
- The value case is strongest on large stones and multi-stone pieces and weakest on resale. Buy lab-grown for the jewellery, not as an investment.
What a Lab-Grown Diamond Is - and What It Isn't
Diamond is a specific arrangement of carbon atoms in a cubic lattice. That arrangement is what makes it the hardest natural material, gives it the refractive index that produces the sparkle, and makes it chemically inert. A lab-grown diamond has that same lattice, built by human equipment instead of geological time. Under a microscope, on a thermal conductivity tester, in a piece of jewellery on a hand - it is a diamond.
This is not only a marketing position. In 2018 the US Federal Trade Commission revised its Jewelry Guides and removed the word natural from its definition of a diamond, on the reasoning that a laboratory-created stone with identical composition is still a diamond. Those Guides are advisory rather than a statute - they set out how the FTC reads its general prohibition on deceptive practices - but the practical effect is the same: a seller who obscures a stone's origin is exposed, which is why reputable listings say lab-grown, lab-created, or laboratory-grown somewhere prominent.
The confusion worth clearing up is with simulants. Cubic zirconia and moissanite are not diamonds at all - different chemistry, different hardness, different optics. A lab-grown diamond and a cubic zirconia have almost nothing in common except transparency. We come back to this below, because the terms get used loosely in marketplace listings.
The Two Ways They Are Made: HPHT and CVD
High Pressure High Temperature growth does what the name says. A small diamond seed and a carbon source are placed in a press that reproduces mantle conditions - immense pressure at temperatures well over a thousand degrees Celsius - and carbon crystallises onto the seed. HPHT is the older method, and it is also used to treat both mined and grown stones to improve their colour.
Chemical Vapour Deposition works at low pressure instead. A seed plate sits in a chamber filled with carbon-rich gas, usually methane and hydrogen. Energy breaks the gas apart, and carbon settles onto the plate atom by atom, growing the crystal upward in layers. CVD gives more control over the growing conditions and now dominates the larger colourless stones submitted for grading. By sheer unit count, global production is still weighted toward HPHT, largely because the melee stones used in pave and eternity settings are produced that way at scale.
Does the method change what you are buying? Slightly, and mostly at the margins. HPHT stones can retain metallic inclusions from the growth medium; CVD stones more often show strain patterns and occasionally a faint brown cast before post-growth treatment. Both routes produce stones across the full range of grades, and a graded certificate tells you far more about a specific stone than its growth method does. If a listing states one method as though it were a quality claim, treat it as a marketing point rather than a specification.
How They Are Graded and Certified
Lab-grown diamonds are assessed on the same four criteria as mined stones - carat, colour, clarity, and cut - but how those results are reported has changed more than once, and this is the single most out-of-date thing in most articles on the subject. Laboratories initially used broad descriptive ranges for grown stones. Around 2020 they moved to the same D-to-Z colour and Flawless-to-I3 clarity scales used for mined diamonds, so a G colour grown stone meant exactly what a G colour mined stone meant.
Then GIA reversed course. From 1 October 2025 its lab-grown reports no longer carry letter colour grades or Flawless-to-I3 clarity grades at all; stones are described as Premium, Standard, or given no designation, on the reasoning that the overwhelming majority of submissions cluster in the top few grades and the fine distinctions carried little information. The International Gemological Institute, which certifies most lab-grown volume and is the report you will see most often on marketplace listings, continues to issue full letter grades. GCAL is known for light-performance analysis alongside standard grades. The practical consequence for a buyer is that two certificates for comparable stones may now be written in different languages - check which system yours uses before comparing anything.
Whichever laboratory issued it, a report from a named laboratory means the stone was assessed by someone other than the seller, and that is the entire point. Most certified grown stones carry a laser inscription on the girdle - the thin band around the widest part of the stone - recording the report number and often the words lab grown. It is invisible without magnification and it is how a jeweller confirms that the stone in the setting is the stone on the certificate. When a listing states grades but names no laboratory, you are being told the seller's opinion. That distinction is why our studs guide and eternity band roundup both weight certification heavily.
Lab-Grown vs Moissanite vs Cubic Zirconia
Moissanite is silicon carbide. It is very hard - just below diamond on the Mohs scale - and durable enough for daily wear, but it is optically different in a way most people can see once they know to look. Its refractive index is higher and it is doubly refractive, which produces more coloured fire and, in larger sizes, a slightly disco flash that diamond does not have. It is a good stone honestly described and a poor one sold as a diamond.
Cubic zirconia is zirconium dioxide. It is softer than either diamond or moissanite, noticeably heavier for its size, and it loses polish and accumulates surface abrasion over a few years of regular wear rather than over decades. Worth being accurate about the cause of the clouding people describe in old cubic zirconia: it is micro-abrasion of the surface, not a change inside the stone, and a diamond of either origin does not do it. Cubic zirconia has a legitimate place in costume jewellery and travel pieces and no place in something you intend to keep.
The practical test is the paperwork, not the eye. A lab-grown diamond will have a diamond grading report from a named laboratory. A moissanite will have a manufacturer's certificate or none. A cubic zirconia will have neither. If a listing at a suspiciously low price says diamond simulant, diamond alternative, or diamond-like, it is telling you it is not a diamond.
Where the Value Argument Holds Up - and Where It Doesn't
The savings are real and they compound with size. Because growth capacity scaled up quickly, the gap between grown and mined pricing widened rather than narrowed, and it widens further as carat weight increases - a mined stone's price climbs steeply with size, while a grown one climbs far more gently. On multi-stone pieces the effect multiplies: an eternity band or a tennis bracelet uses a dozen or more stones, and the difference stops being a discount and becomes the reason the piece is buyable at all.
The place the argument fails is resale. Grown diamond prices have fallen substantially as production expanded, and there is no established secondary market to speak of - a stone bought two years ago may not fetch anything like its purchase price. Mined diamonds are a poor financial asset too, but grown stones are a worse one, and anyone telling you otherwise is selling something.
So the honest framing is this: buy a lab-grown diamond because it gets you a larger, better-graded stone in a nicer setting for money you were going to spend on jewellery anyway. Do not buy it as a store of value. If you are weighing the two origins against each other for a significant purchase, our side-by-side comparison goes through the trade-offs in detail.
Frequently Asked Questions
Are lab-grown diamonds real diamonds?
Yes. They have the same carbon crystal structure, hardness, and optical properties as mined diamonds, and since 2018 the US Federal Trade Commission's Jewelry Guides no longer define a diamond as necessarily natural. What sellers must do is disclose the origin clearly.
Can a jeweller tell a lab-grown diamond from a mined one?
Not reliably with a loupe or a standard thermal tester - both read as diamond, because both are diamond. Some stones do give themselves away under magnification, such as metallic flux inclusions in HPHT material or strain patterns visible under cross-polarised light, but a clean stone needs specialised screening instruments. In everyday practice, identification comes from the girdle inscription and the grading report.
Do lab-grown diamonds get cloudy or lose sparkle over time?
No. That is a property of cubic zirconia, which is much softer and abrades with wear. A lab-grown diamond is as hard as any other diamond and will look the same in thirty years, assuming the setting is maintained. Cloudiness in an older piece is almost always accumulated soap and skin oil, which cleaning fixes.
Which is better, HPHT or CVD?
Neither, as a general rule. Both methods produce stones across the whole quality range, and a report on the specific stone tells you far more than its growth method does. CVD dominates the larger colourless stones and HPHT still accounts for most melee by unit count, but that is a production fact rather than a quality ranking. Treat a listing that promotes one method as a quality claim with mild scepticism.
Do lab-grown diamonds hold their value?
No, and it is worth being direct about it. Prices have fallen significantly as production capacity grew, and there is no meaningful resale market. Buy one for the jewellery it lets you afford, not as an investment.
Is a lab-grown diamond a more ethical choice?
It avoids the sourcing questions attached to mining, which matters to many buyers, but growth is energy-intensive and the footprint depends heavily on the electricity that powers the reactor. Some producers publish renewable-energy sourcing; most do not. It is a reasonable preference to hold, and an oversimplification to treat as settled.
Should the certificate come from IGI or GIA?
Either is a genuine independent report, but as of October 2025 they are no longer directly comparable. IGI certifies most lab-grown volume and still issues letter colour grades and standard clarity grades. GIA now reports lab-grown stones only as Premium, Standard, or unclassified. If you are comparing two stones, make sure you are comparing like with like - and if a listing quotes a letter grade alongside a GIA lab-grown report number, ask questions.
Related Guides
How We Research
Our guides draw on manufacturer documentation, established industry practice, and what we learn testing and researching products for our buying guides. Where practice varies or opinion divides, we say so rather than pretending at consensus.
Buying note: Ask for the report number before you buy, then look it up on the laboratory's own site. A genuine report can be verified online in under a minute, and a seller who cannot produce a number has told you what you need to know.