Lab-grown vs natural diamond: what is the same, what is different

What is the same

• The material. Same composition, same crystal structure, so the same hardness, toughness, refractive index, dispersion and density. A well-cut laboratory-grown round returns the same brightness and fire as a well-cut mined one, because the optics belong to the material, not to where it grew.
• The look. No one separates them by eye or by loupe. That is why screening instruments exist.
• The tester. A thermal probe reads both as diamond, because thermal conductivity is a property of diamond.
• The bench. Setting, polishing, ultrasonic, steam, rhodium, retipping and sizing with stones in place all follow the diamond rules you already use. Like any diamond it will etch or burn if held at red heat in open air, so keep the flux or boric acid coat on and the torch moving.
• The grading. The same D–Z colour and FL–I3 clarity scales, graded by the same laboratories. At melee sizes both are sorted and graded as a parcel, not stone by stone.
• The wear. Neither clouds, fades or dulls. Both chip the same way at a thin girdle if they take a knock.

What is different

• Origin and time. A mined diamond formed in the mantle over geological time. A laboratory-grown diamond grew in weeks, either under high pressure and temperature in a metal flux (HPHT) or deposited from a carbon plasma onto a seed plate (CVD). Both methods grow single-crystal diamond from carbon; nothing is coated or composite.
• Price and supply. DE colour, VS–VVS melee in every calibrated size is a stock item in laboratory-grown diamond at a price mined diamond cannot approach. The same grade in mined melee is scarce, and most production jewelry uses G–H / SI mined melee instead.
• Identification. A screening instrument passes most mined stones and refers everything else: laboratory-grown stones and the small share of mined diamonds that, like them, contain no nitrogen (type IIa). A gem laboratory then makes the call from fluorescence imaging and spectroscopy, where growth patterns differ: HPHT stones show cubic and octahedral growth sectors, CVD stones show layered growth, and mined stones show the irregular growth record of a natural crystal. Under the microscope the inclusions differ too (metallic flux in HPHT, pinpoints and graphite in CVD, mineral crystals in mined). Certified laboratory-grown stones of 1 ct and above usually carry a girdle inscription and a report marked laboratory-grown.
• Disclosure. Under the FTC Jewelry Guides (16 CFR Part 23) and ISO 18323, the word diamond on its own means a mined diamond. Laboratory-grown material must be described as laboratory-grown, laboratory-created or lab-grown diamond, with the qualifier right next to the word diamond, and must never be called real, genuine or natural. This applies to your invoice, your appraisal and your website as much as to ours.
• Value over time. Laboratory-grown prices have fallen steeply over the past decade as production scaled, and there is little resale market. A mined stone has a trade-in market, at a discount to retail. Neither is an investment at retail prices, but say this plainly so the client hears it from you: laboratory-grown is bought for what it is and what it costs, not as a store of value.
• Claims you should not make. Words like sustainable or eco-friendly need substantiation under the FTC's Green Guides, and the FTC sent warning letters to laboratory-grown sellers over exactly such claims in 2019; growing diamond takes a great deal of electricity and the supply chain varies. We do not make those claims and suggest you do not either.

At the bench: two things to know

Combined testers and HPHT stones. Some HPHT-grown colourless stones carry traces of boron and conduct electricity. A combined thermal-and-electrical tester can occasionally misread such a stone as a simulant. The thermal reading alone says diamond; a screening instrument settles it.

Temporary colour shift in some CVD stones. A small share of CVD-grown stones shift colour for a while, towards grey-blue or brown, after torch heat or strong ultraviolet, and return to normal over hours to days, faster in daylight. If a stone looks off straight after retipping, let it sit before judging it. This is a known behaviour of the material, not damage.

Next to a mined centre stone

Laboratory-grown melee around a mined centre is the usual use for it, and it works: the side stones match the centre in colour, brightness and tester response, and they age the same way. Two practical notes. Our melee is DE colour; beside a G–H centre it reads a touch whiter, which most clients see as a brighter ring, but beside a J or warmer centre the contrast can show, so judge it on the piece. And disclose it: the invoice and the appraisal should say laboratory-grown diamond melee, so that when a screener refers the side stones at the next appraisal, the appraiser is expecting it.

Invoice and appraisal wording

Write it as laboratory-grown diamond or lab-grown diamond, with the qualifier next to the word diamond, every time it appears: on the quote, the invoice, the appraisal and the insurance schedule. Melee reads well as "laboratory-grown diamond melee, DE colour, VS–VVS, 1.5 mm, 20 stones". Do not write real, genuine, natural or cultured for laboratory-grown stones, and do not write diamond alone. For a mined stone, diamond is the correct word. For appraisal, value laboratory-grown stones on their own market rather than on mined-diamond price lists, and make sure the insurer's schedule carries the laboratory-grown designation.

Questions jewelers ask

Is a laboratory-grown diamond a real diamond?

By composition, structure and every physical and optical property, it is diamond. The FTC reserves the words real, genuine and natural for mined stones, so the correct name is laboratory-grown diamond, and that is what goes on the invoice.

Can a jeweler tell laboratory-grown from mined?

Not by eye or loupe, and a thermal tester reads both as diamond. A screening instrument passes most mined stones and refers laboratory-grown ones (and the few nitrogen-free mined stones) for laboratory testing, where fluorescence imaging and spectroscopy give the final answer.

Does laboratory-grown diamond hold its value?

Prices have fallen as production has scaled and there is little resale market, whereas mined diamond has a trade-in market at a discount to retail. Sell laboratory-grown diamond on what it is and what it costs, not as a store of value.

Can I set laboratory-grown melee around a mined centre stone?

Yes, and it is the most common use. It matches a mined centre in colour, brightness and tester response. Disclose it on the invoice and appraisal as laboratory-grown diamond melee.

Does it behave the same at the bench?

Yes: the same setting, polishing, ultrasonic, steam and torch rules as mined diamond. Two notes: some HPHT stones conduct electricity and can confuse a combined thermal-and-electrical tester, and some CVD stones shift colour temporarily after heat or strong UV and recover over hours to days.

Is the melee graded?

Melee is sorted and graded as a parcel, DE colour and VS–VVS clarity, the same way mined melee is handled in the trade. Stones of 1 ct and above can be supplied with a laboratory report; ask when you enquire.