Understanding Diamonds: Natural vs Lab-Grown

Diamonds have two origins and one material. A lab-grown diamond and a mined diamond are both diamond — the same carbon, crystallised the same way — and what separates them is how each came to exist, not what each one is.

That is not a marketing position. It is how the definition is written into US trade guidance, and it settles most of the arguments buyers and traders have about the two. What follows is what can be established from the two authorities that grade these stones, GIA and IGI, and from the Federal Trade Commission’s Jewelry Guides. Where a common claim could not be sourced to any of them, it has been left out rather than repeated, and those omissions are named where they fall.

If you have already decided on a lab-grown stone, the buying side — the 4Cs, reading a report, metals, settings and price — is covered in our complete guide to buying lab-grown diamond jewelry. This article stays with the comparison.

The Definition Settles Most of It

Under the FTC’s Jewelry Guides, a diamond is defined by what it is, not by where it came from: “a mineral consisting essentially of pure carbon crystallized in the isometric system”, with a hardness of 10, a specific gravity of approximately 3.52 and a refractive index of 2.42 (16 CFR § 23.12(a)).

Nothing in that definition mentions origin. A lab-grown stone that meets it is, by the definition, a diamond — and the Guides identify only two things that would make the unqualified word “diamond” deceptive: an object that does not meet the definition, or one that has not been “symmetrically fashioned with at least seventeen (17) polished facets” (§ 23.12(b)).

IGI says the same thing in plainer language. Lab-grown diamonds are “optically, chemically, and physically identical to natural diamonds”, and once cut and polished they are indistinguishable from them “without examination by trained experts using sophisticated instruments”.

Where They Differ

How each one forms

Natural diamonds formed billions of years ago, deep within the earth. Lab-grown diamonds are grown above ground in a controlled environment by one of two methods: High-Pressure High-Temperature (HPHT), which replicates the conditions of natural formation, or Chemical Vapor Deposition (CVD), which builds the crystal from carbon separated out of a hydrocarbon gas. IGI puts the growth time at one to four weeks.

That single difference — billions of years against weeks — is the origin of every other practical difference between the two.

What is identical

• Composition and crystal structure. Both are carbon crystallised in the isometric system (§ 23.12(a); IGI).
• Optical properties. IGI states the refractive index and optical qualities are identical, and that both are assessed on the same colour and clarity scales.
• Hardness. Both rank 10 on the Mohs scale, the top of it. For scale, corundum — the mineral that gives us ruby and sapphire — ranks 9, and IGI notes that diamonds exhibit nearly ten times its hardness.
• Grading method. Both are graded on the same 4Cs: carat, colour, clarity and cut (IGI).

The differences, side by side

	Natural diamond	Lab-grown diamond
Origin	Formed deep within the earth	Grown in a controlled environment
Formation time	Billions of years	One to four weeks
Growth method	Geological	HPHT or CVD
Composition	Carbon, isometric crystal	Carbon, isometric crystal
Mohs hardness	10	10
Graded on	The 4Cs	The 4Cs
Identification	Requires a gem laboratory with specialised instruments	Requires a gem laboratory with specialised instruments
Price	Higher	Typically lower
Typical documentation	Diamond grading report	A different document — see below

Sources: 16 CFR § 23.12(a); IGI, Lab Grown Diamonds; GIA, Laboratory-Grown Diamond Services.

The Paperwork Is Genuinely Different

This is the part most comparisons miss, and the part that matters commercially.

GIA does not issue a lab-grown diamond the same report it issues a natural one. For loose colourless to near-colourless lab-grown stones of 0.15 carats or more, GIA issues a Laboratory-Grown Diamond Quality Assessment, which classifies the stone as Premium or Standard rather than placing it on the natural-diamond grade scale. The stone’s girdle is laser-inscribed with the term “Laboratory-Grown” and the assessment number. Coloured lab-grown stones receive a separate, digital-only report that also assesses growth type and any post-growth treatment.

So the question worth asking is not “does it come with a certificate?” but “which document is it, and what does it say?” A lab-grown quality assessment and a natural-diamond grading report are different instruments, and the difference is deliberate.

What a Seller May and May Not Say

The Guides allow a lab-grown stone to be called a diamond, and they are specific about how its origin must be conveyed.

The word “cultured” may be used to describe a laboratory-created diamond only when it is accompanied by a clear and conspicuous disclosure — for example “laboratory-created”, “laboratory-grown”, or “[manufacturer name]-created” (§ 23.12(c)(3)). IGI makes a related point for the trade: it uses the term “lab grown diamonds”, notes that the FTC considers wording like that “more precise and less confusing” than “synthetic”, and warns that some countries require the unabbreviated “laboratory grown diamond” or a different term altogether.

The practical rule for a buyer: a lab-grown stone may be sold as a diamond, but it must not be allowed to pass as a mined one.

Can the two be told apart?

Not by eye, and not reliably at a jeweller’s bench. IGI’s position is that only specialised instruments at a grading institute can decisively separate lab-grown from natural stones, and that the tools available to the jewellery trade can raise a suspicion but cannot prove origin. IGI also notes that it was the first gemological institute to grade lab-grown diamonds.

Price, Without Guesswork

This article quotes no prices, and the omission is deliberate. Prices in both categories move, vary by market, and depend on the individual stone’s 4Cs; no laboratory publishes a price list.

What can be stated is the direction. IGI’s position is that lab-grown diamonds, and lab-grown diamond jewelry, typically command lower prices than equivalent natural diamonds — and that as production technology is refined, that cost advantage may widen without a loss of quality or beauty.

The practical consequence for a budget: the same money reaches a larger or higher-graded lab-grown stone than a natural one.

On resale, this article is deliberately silent. An earlier version of this page asserted that natural diamonds hold a robust resale market and lab-grown a developing one. Neither GIA nor IGI publishes resale data for either category, and the claim could not be sourced — so it has been removed rather than restated. Treat a confident resale figure from any source as unverified unless it is dated and attributed.

Sustainability and Ethics: What Can Honestly Be Claimed

Environment and ethics are where these two categories are most often described in ways the sources do not support.

IGI’s answer to whether lab-grown diamonds are sustainable is unusually direct: no, most lab-grown diamonds are not fully sustainable. The energy demands of the presses and reactors often depend on fossil fuels, so “eco-friendly” and “green” do not commonly apply as category-wide claims. IGI adds that some producers do use wind, solar or hydroelectric power, and that those practices are often backed by third-party certification — which means a sustainability claim is worth something only when it is specific to a producer and evidence-backed.

On ethics, IGI’s position is narrower and better supported: lab-grown diamonds are produced in safe, controlled conditions and have no historic association with conflict.

What this article does not do is compare mining’s land, water and carbon impact against laboratory production. No GIA or IGI source supports a quantified comparison, and an unquantified one would be an assertion rather than a fact.

Choosing Between Them

The two stones are the same material, so the decision is not about quality. It comes down to four questions.

Does origin matter to you? For some buyers a stone formed over billions of years carries meaning. That is a genuine reason to choose natural — a reason about meaning rather than about the stone.

What does your budget need to buy? Because lab-grown stones typically cost less per stone (IGI), the same budget reaches a larger stone or a higher grade. If face-up size matters more to you than origin, that difference is the whole decision.

Which document do you want to hold? If you want a natural-diamond grading report, you want a natural diamond — GIA’s lab-grown documentation is a different instrument. If what you want is independent verification that the stone is what the seller says it is, either category can provide it.

Who is it for, and what will they be told? The Guides require lab-grown origin to be disclosed clearly. Whichever you choose, buy from a seller who states which one it is without being asked.

Where to look: lab-grown diamond engagement rings, lab-grown diamond earrings and lab-grown diamond necklaces each list pieces with their stone and metal stated.

Frequently Asked Questions

Are lab-grown diamonds real diamonds?

Yes. The FTC’s definition of a diamond is about composition, not origin — essentially pure carbon crystallised in the isometric system, hardness 10, specific gravity approximately 3.52, refractive index 2.42 (16 CFR § 23.12(a)). IGI states that lab-grown diamonds are optically, chemically and physically identical to natural diamonds.

Are lab-grown diamonds synthetic?

IGI’s answer is “technically yes” — they are made by chemical synthesis — but the institute adds that the term can be misleading, and notes that the FTC considers “lab grown diamond” more precise and less confusing. The Guides permit the word “cultured” only with a clear and conspicuous qualifier such as “laboratory-created” or “laboratory-grown” (§ 23.12(c)(3)).

Can a jeweller tell a lab-grown diamond from a natural one?

Not decisively. IGI’s position is that the tools available to the jewellery trade can identify a suspected lab-grown diamond, but that only a grading institute with specialised instruments can prove origin. Both IGI and GIA provide that service.

Are lab-grown diamonds cheaper?

Typically, yes. IGI’s position is that lab-grown diamonds and lab-grown diamond jewelry command lower prices than equivalent natural diamonds. This article quotes no figures, because prices move with the market and depend on the individual stone’s 4Cs.

Are lab-grown diamonds eco-friendly?

Not as a category, on IGI’s own statement: most lab-grown diamonds are not fully sustainable, because the energy for the presses and reactors often comes from fossil fuels. Narrower claims can hold — a specific producer using renewable energy, evidenced by third-party certification.

How is a lab-grown stone’s quality documented?

For loose colourless to near-colourless lab-grown stones of 0.15 carats and above, GIA issues a Laboratory-Grown Diamond Quality Assessment, classifying the stone as Premium or Standard and laser-inscribing the girdle with “Laboratory-Grown” and the assessment number. How to read that document, and how to weigh the 4Cs when buying, is covered in our complete guide to buying lab-grown diamond jewelry.

Sources

• Federal Trade Commission — 16 CFR Part 23, Guides for the Jewelry, Precious Metals, and Pewter Industries (eCFR, current through 8 October 2026; § 23.12 source: 83 FR 40667, 16 August 2018). Used for: the definition of “diamond” and the seventeen-facet requirement in § 23.12(a) and (b), and the permitted use of “cultured” with a qualifying disclosure in § 23.12(c)(3).
• IGI — Lab Grown Diamonds (igi.org/lab-grown-diamonds/). Used for: the one-to-four-week growth time; optical, chemical and physical equivalence to natural diamonds; grading on the same 4Cs; the HPHT and CVD growth methods; Mohs 10 for both natural and lab-grown diamonds with corundum at 9; identical refractive index; the requirement for specialised instruments at a grading institute to determine origin; the terminology position, including the FTC’s preference and the differing national requirements; the price position; the statement that most lab-grown diamonds are not fully sustainable; and the position on conflict-free production.
• GIA — Laboratory-Grown Diamond Services (gia.edu/gem-lab-service/laboratory-grown-diamond). Used for: the Laboratory-Grown Diamond Quality Assessment and its Premium/Standard classification; the 0.15-carat minimum; the “Laboratory-Grown” girdle inscription; and the separate coloured lab-grown report covering growth type and post-growth treatment.