Lab Grown Diamond Certification: IGI, GIA and What to Check

925 sterling silver jewellery, set with lab grown diamonds and made in our own Shenzhen workshop.

Posted on October 6, 2026by Taylor James

The most common misreading of a lab grown diamond report is that it certifies value. It does not. A report records identity, measurements and grades for one stone on one date; it says nothing about price, nothing about what a retailer should charge, and nothing about what the stone will be worth later. Buyers who understand the document as a technical record rather than a valuation handle it well, and they know which fields to read first. This page covers what a report is, how the two laboratories buyers encounter most often differ, and what to verify before a stone is committed.

Last updated: October 11, 2026

Table of Contents

Does a lab grown diamond need a certificate?

For any stone sold on its own, yes — a report from a recognised laboratory is the practical minimum.

Origin cannot be confirmed with a handheld tester, and neither can treatment status, so without documentation the buyer is relying entirely on the seller’s description. A report converts those claims into a verifiable record with a number that can be checked against the laboratory’s own database. That is the function it serves.

The exception is melee. Very small stones are normally graded and specified at parcel level because a per-stone report would cost more than the stone, and the disclosure moves to the parcel documentation and the finished product description.

What a grading report is, and what it is not

It is a technical description of one stone; it is not a valuation, an appraisal or a guarantee.

An appraisal estimates value for insurance or resale purposes and is issued by a valuer, often using a report as an input. A guarantee would require the laboratory to stand behind the stone’s future condition, which no grading laboratory does. A report also describes the stone at the moment of examination: if it is later re-cut, damaged or treated, the document no longer describes it.

Three consequences follow. Do not compare two stones using reports issued years apart without checking they still match the stones. Do not assume a report number implies quality. Do not treat a report as evidence of origin beyond what it states.

IGI and GIA compared

Both are established laboratories whose reports are accepted in the trade; they differ in scope, scale and how buyers use them.

GIA is a research and education institute with a grading laboratory operation, and its reports are widely used as the reference standard in the mined diamond trade. IGI operates a larger network of grading locations and grades a substantial share of the world’s laboratory-grown diamonds, which makes its reports the ones buyers encounter most often in that segment. Both apply the same colour and clarity scales, both disclose laboratory-grown origin, and both publish verification services.

Point	GIA	IGI
Primary orientation	Research institute with grading laboratory	Commercial grading laboratory network
Report acceptance	Widely referenced in mined diamond trade	Common across lab grown production
Grading scales	Colour and clarity scales	Same colour and clarity scales
Origin disclosure	States laboratory-grown	States laboratory-grown
Verification	Online report check	Online report verification
Practical use	Reference grading for single stones	High-volume parcel grading and single stones

The fields that decide value

Measurements, proportions, polish, symmetry, fluorescence and treatment status.

Measurements give the physical size in millimetres, which is what determines how large the stone looks — not the carat weight on its own. Proportions describe the angles and percentages that control light return. Polish and symmetry describe the quality of the finish. Fluorescence records how the stone reacts to ultraviolet light, and strong fluorescence can affect appearance in some lighting. Treatment status, where applicable, is a value-relevant disclosure.

These fields are also where two stones of identical headline grade separate, which is why reading the detail is more useful than reading the grade line.

Close view of a diamond grading document used to verify stone identity, measurements and grades before purchase — The report number is the part a buyer can independently verify.

Wording to watch

Laboratory grown, synthetic, created and treated are not interchangeable in every document.

Standards bodies use terminology that distinguishes origin clearly, and the term used on a report may differ from the term used in a shop’s product description. The mismatch is usually a translation of register rather than a deception, but it becomes a problem when an invoice, a customs description and a product page describe the same stone three different ways.

The other wording to read carefully is treatment. A stone that has been treated after growth can still be a good stone, but the disclosure should be present on the report and repeated in the supplier’s documentation.

How to verify a report number

Take the number from the document to the laboratory’s own verification service.

Both major laboratories publish online verification, and the check takes seconds. What it confirms is that the number corresponds to a report the laboratory issued, along with the recorded characteristics of that stone. What it does not confirm is that the physical stone in front of you is the stone the report describes — that requires matching the measurements and, for higher-value stones, a fresh examination.

For parcels, verification is normally done on sample stones rather than every stone, which is why the sample sizes and the selection method belong in the purchase terms. If the stones are being set into silver, the silver lab grown diamond checklist sets out what to confirm in the same document.

Gemstone and jewellery documentation check shown alongside a stone, illustrating how buyers verify identity and disclosure — Verification is a documents check as much as a stone check; the number has to match the goods.

Where reports can mislead buyers

Mostly through absence: of a field, of a grade, or of a document.

A shorter report format carries fewer fields, so a stone described as “certified” may be documented with an identification report rather than a full grading report. A grade range rather than a single grade leaves the exact position undefined. A report that predates a re-cut or a setting job describes a stone that no longer exists in that form.

None of these are failures of the laboratory; they are failures of the buyer’s specification or of the seller’s description. Naming the report format in the purchase order removes the first two.

What an appraisal is, and why it differs

An appraisal is a valuation document, produced for a specific purpose and date.

Appraisals are prepared for insurance schedules, resale, estate purposes or customs, and their numbers depend on the assumptions written into them: replacement value, market value, wholesale or retail basis. Two appraisals of the same piece can differ substantially without either being wrong, because they answer different questions.

For a manufacturer or brand, the practical implication is that the grading report travels with the stone and the appraisal travels with the transaction.

What a manufacturer should hand over per parcel

Documentation should be specified at order stage and checked on arrival.

The minimum for a single stone is the report, a statement of growth method where available, and a statement of treatment status. For a parcel, it is the parcel specification with size range, colour and clarity bands, matching tolerance, and the report or grading basis applied to it. For finished pieces going to a consumer, it is the stone documentation plus the metal specification and hallmarking.

At our end, parcels are selected and matched against the agreed tolerance, and the documentation that accompanies each shipment is confirmed against the purchase order before dispatch.

FAQ

Is a GIA certificate better than an IGI certificate?

Neither is inherently better as a grading document. Both apply the same colour and clarity scales and both disclose laboratory-grown origin, and both publish verification services. GIA is more often used as a reference in the mined diamond trade, while IGI grades a large share of laboratory-grown production. What matters is that the report format matches the use case.

How do I read a diamond certificate?

Start with identity and measurements, then proportions, then colour, clarity, polish and symmetry, then fluorescence and treatment status. Measurements tell you how large the stone looks; proportions tell you how it performs; the grade line tells you the summary. Read the detail before the summary.

Do lab grown diamonds come with certificates from the factory?

Larger stones normally ship with a report from a recognised laboratory. Melee usually ships with a parcel specification rather than individual reports, because a report per stone would cost more than the stone itself. If a programme requires individual reports on small goods, that belongs in the purchase order.

Can a certificate be faked?

A document can be copied, which is why verification happens through the laboratory’s online service rather than by looking at the paper. Verification confirms that the number and recorded characteristics exist. It does not prove the physical stone is the one described, so measurements should be checked against the stone on higher-value purchases.

Sources and further reading

Next step: If your programme needs a specific report format, tell us which one and we will confirm what each stone or parcel will carry, along with growth method and treatment status, before the order is placed. Loose stones, matched parcels and finished pieces are all supplied OEM/ODM. Contact vinico@zkzdiamonds.com or WhatsApp +86 135 3037 8229.

Part of our lab grown diamonds guide.