Lab-Grown vs Mined Diamonds: The Honest Comparison

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A lab-grown diamond and a mined diamond are the same material: pure crystallised carbon in a cubic lattice, with identical hardness, refractive index and brilliance. Neither a jeweller's eye nor a 10x loupe can separate them, because there is nothing to separate — the difference is where the crystal formed, not what it is. What genuinely differs is origin, environmental footprint and price.

Key takeaways

• Lab-grown and mined diamonds are physically, chemically and optically identical — both are real diamonds.
• The US Federal Trade Commission recognised lab-grown stones as diamonds in 2018.
• They are graded by the same laboratories, though GIA changed how in October 2025.
• Telling them apart requires specialised laboratory instruments — a standard diamond tester passes both.
• A lab-grown stone of matching specification commonly costs 70–90% less at retail.
• How a diamond looks is decided by cut, not by origin.

Are lab-grown diamonds real diamonds?

Yes — and this is settled both gemologically and in regulation. A diamond is defined by its composition and crystal structure: carbon atoms arranged in an isometric cubic lattice. A lab-grown diamond meets that definition exactly. In 2018 the US Federal Trade Commission revised its jewellery guides to remove the word "natural" from the definition of a diamond, formally recognising that a laboratory-created stone is a diamond rather than an imitation of one.

That distinction matters because it separates lab-grown diamonds from simulants — materials that merely resemble diamond. Cubic zirconia and moissanite are simulants: different chemistry, different hardness, different optical behaviour. A lab-grown diamond is not in that category at all. We compare them directly in lab-grown diamonds vs moissanite and lab-grown vs cubic zirconia.

What is identical

Everything you can measure about the stone itself. Both are pure carbon in the same lattice. Both rate 10 on the Mohs hardness scale — the hardest known natural material, and the reason a diamond survives daily wear for a lifetime. Both share a refractive index of about 2.42, which is what produces diamond's characteristic brilliance, and the same dispersion, which produces its fire. Both conduct heat identically.

They are also graded on the same 4Cs by the same laboratories, using the same scales and the same equipment. If those grades are new to you, start with the 4Cs explained without jargon.

What is different

The origin story, and what it costs the world to produce.

A mined diamond crystallised over a period usually measured in the billions of years, roughly 150 km below the surface, and reached us because ancient volcanic eruptions carried it up through kimberlite pipes. A lab-grown diamond crystallises over weeks in a reactor that recreates those conditions of temperature, pressure and chemistry. Both processes produce diamond. One took geological time and required moving very large volumes of rock to recover a comparatively small quantity of gem-quality material; the other takes weeks and consumes electricity.

The honest environmental comparison is a little more nuanced than either industry's marketing suggests: growing diamonds is energy-intensive, so the footprint depends substantially on how that electricity is generated. What is not in dispute is that reactor growth avoids the land disturbance, tailings and water use that extraction involves. We look at the evidence properly in are lab-grown diamonds sustainable.

How are lab-grown diamonds actually made?

Two methods dominate, and both begin with a thin diamond seed.

HPHT — high pressure, high temperature — mimics the geology directly, crystallising carbon onto the seed under immense pressure and heat. It typically produces a cuttable crystal in a few days to a few weeks depending on target size.

CVD — chemical vapour deposition — works at lower pressure, using microwave energy to break down a carbon-rich gas so that carbon atoms settle onto the seed layer by layer. A cuttable CVD crystal usually takes around three to four weeks, and some stones then undergo a post-growth HPHT treatment to refine colour before cutting.

Neither method is inherently superior; both produce stones across the full quality range, and the finished grade on the report is what matters rather than the growth route. Our full explanation is in how lab-grown diamonds are made: CVD vs HPHT.

Lab-grown vs mined, side by side

Property	Lab-grown	Mined
Chemical composition	Pure carbon, cubic lattice	Pure carbon, cubic lattice
Hardness	Mohs 10	Mohs 10
Refractive index	≈ 2.42	≈ 2.42
Brilliance and fire	Identical	Identical
Graded on the 4Cs	Yes — IGI on the full scale	Yes
Formation time	Weeks in a reactor	Typically billions of years
Distinguishable by eye or loupe	No	No
Origin disclosed on report	Yes, plus girdle inscription	Yes
Price at matching specification	Commonly 70–90% less	Baseline

Can anyone tell the difference?

Not by looking, and not with the tools most jewellers keep on the counter. The handheld "diamond testers" sold for retail use measure thermal conductivity, and since a lab-grown diamond conducts heat exactly as a mined one does, it registers as diamond — correctly, because it is one.

Separating the two requires gemological laboratory instruments that look at growth features rather than material properties: photoluminescence spectroscopy, and fluorescence imaging of the kind used to reveal the distinctive growth striations left by CVD or HPHT crystallisation. This is exactly what the certifying laboratory does, which is why origin appears on the report — and why IGI and GIA both laser-inscribe "laboratory-grown" on the girdle of the stones they certify. Nobody is being fooled; disclosure is built into the paperwork.

Why do lab-grown diamonds cost less?

Not because the stone is lesser. Because the supply chain behind it is shorter and its supply is not constrained.

A mined diamond's price carries exploration, extraction, a long chain of intermediaries, and a supply deliberately managed for scarcity. A lab-grown diamond's price carries the reactor, the energy, the cutting and the certification. Removing the first set of costs does not change the crystal — it changes the arithmetic between you and it. A stone of matching specification commonly costs 70–90% less at retail, and the gap is widest at exactly the large, high-grade specifications that are rarest in the ground.

That last point is the whole reason our standard is possible. A D–E, VVS, Triple Excellent stone at three carats is genuinely rare in mined form and priced accordingly; grown, it is simply a specification you can ask for. We break the retail arithmetic down in what a lab-grown ring is really charging you for, and cover Canadian specifics in buying lab-grown diamonds in Canada.

What about resale and value?

Here we will be direct, because a lot of writing on this subject is not. Diamonds of any origin are poor financial instruments — mined stones typically resell for a fraction of their retail price too, since you are selling into a wholesale market you originally bought retail from. Lab-grown stones sit in a younger market with less established secondary pricing.

The sensible conclusion is not that one holds value better than the other; it is that an engagement ring is not an investment vehicle and should not be chosen as one. The genuine value in lab-grown is what you get to wear: a materially larger, higher-graded stone for a given outlay. We treat the question honestly in lab-grown diamond resale value.

What actually matters for your ring

Cut. Then cut. Then cut.

A three-carat, VVS1, D-colour stone with mediocre proportions will look duller than a smaller stone cut to Triple Excellent, because proportions decide whether light entering the top comes back out of the top. Origin does not appear anywhere in that sentence — a poorly cut mined diamond and a poorly cut lab-grown diamond are equally disappointing. Montare's floor sits at Triple Excellent with ideal table and depth for each shape for exactly that reason; see why Triple Excellent matters.

What we will not say

We will not tell you lab-grown is "better" than mined. They are the same crystal, and a mined diamond carries a history that some people rightly value. Nor will we tell you a lab-grown diamond is an investment, or that it is guaranteed to hold a particular value.

What we will say is this: at the floor Montare insists on — lab-grown, D–E, VVS1–VVS2, Triple Excellent, ideal proportions, three carats minimum, IGI certified — the calculation is straightforward. You are paying for the stone, the craftsmanship and the standard, not for an extraction story. The full standard is on our standards page.

Frequently asked questions

Are lab-grown diamonds real diamonds?

Yes. A lab-grown diamond is pure carbon in the same cubic crystal lattice as a mined diamond, with identical hardness, refractive index and brilliance. The US Federal Trade Commission formally recognised them as diamonds in 2018. They are not simulants like cubic zirconia or moissanite.

Can a jeweller tell lab-grown from mined?

Not by eye, and not with a loupe — they are the same material. Distinguishing them requires laboratory instruments such as photoluminescence spectroscopy and fluorescence imaging, which detect growth features rather than differences in the crystal itself.

Will a diamond tester detect a lab-grown diamond?

A standard handheld tester will identify it as diamond, because it measures thermal conductivity and lab-grown diamonds conduct heat identically. That is a correct result, not a false one. Origin is confirmed by the grading report and the girdle inscription.

How long does it take to grow a diamond?

HPHT growth typically produces a cuttable crystal in a few days to a few weeks depending on the size targeted. CVD growth usually takes around three to four weeks, sometimes followed by a post-growth treatment to refine colour before cutting.

Why are lab-grown diamonds cheaper?

Because the supply chain is shorter and supply is not artificially constrained — not because the stone is lesser. The gap is widest at large, high-grade specifications, which are genuinely rare in mined form but simply a specification you can request in grown form.

Are lab-grown diamonds graded by the same laboratories?

Yes, though not identically any more. IGI grades lab-grown diamonds on the full 4Cs exactly as it does mined stones. Since 1 October 2025 GIA has issued a two-tier Premium or Standard classification for lab-grown instead of specific colour and clarity grades.

Do lab-grown diamonds hold their value?

No diamond is a reliable store of value — mined stones also resell for a fraction of retail, because you sell into a wholesale market. Choose the ring you want to wear rather than a stone to resell; the real value in lab-grown is the size and grade you can actually own.

Do lab-grown diamonds get cloudy over time?

No. Diamond is chemically inert and rates 10 on the Mohs scale, so a lab-grown diamond will not cloud, fade or degrade. What looks like cloudiness is almost always skin oils and soap film on the surface, which ordinary cleaning removes.

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