Introduction
A diamond grading report is only useful if it belongs to the diamond in front of you. Two stones can share identical grades — same carat weight, same colour, same clarity — yet be entirely different diamonds with different inclusions, different proportions, and different market values. The report number is what ties a specific document to a specific stone.
On paper, that number appears in the report header. On the diamond itself, it can be laser-inscribed on the girdle — the narrow band where the crown meets the pavilion. This micro-engraving, invisible to the naked eye but clear under magnification, is the most direct way to confirm that stone and report match.
This article explains how inscription works, which laboratories inscribe by default, how to read the number yourself, and why it matters for identification, resale, and peace of mind. For an overview of what else the report contains, see What a Report Contains.
How Laser Inscription Works
Diamond girdle inscription uses a precisely focused laser beam to etch characters onto the girdle surface. The process does not penetrate deep into the stone — the engraving affects only a microscopic layer of the surface, typically less than a micron in depth. It does not alter the diamond's weight, clarity grade, or structural integrity.
The process
The diamond is mounted in a fixture that holds it steady while a computer-controlled laser traces the report number — and sometimes additional text or symbols — onto the girdle. The laser vaporises a thin line of carbon from the diamond's surface, leaving a faintly frosted inscription against the polished or faceted girdle.
Modern inscription systems use either Nd:YAG lasers or newer fibre lasers, both capable of producing characters small enough that the entire report number fits within a few millimetres of girdle space. The text is typically about 30 to 55 microns tall — roughly half the thickness of a human hair.
What gets inscribed
The minimum inscription is the report number itself (e.g., "GIA 2215432567"). Laboratories may also include their logo or brand mark alongside the number. Some services offer optional personal inscriptions — a date, initials, or a short message — for an additional fee. These personal additions sit alongside the report number and do not replace it.
Which Laboratories Inscribe by Default
Inscription policies vary by laboratory and report type.
GIA
GIA offers two main report formats for natural diamonds:
Diamond Dossier — issued for diamonds that typically fall below approximately 1.00 ct (the exact threshold is determined by GIA's current service offerings). The Dossier includes an abbreviated set of information without a full clarity plot. GIA automatically laser-inscribes the report number on all Dossiers. This is a standard, included feature.
Diamond Grading Report — the full-format report for larger stones, including a clarity plot and proportions diagram. Inscription is optional and available for an additional fee. Many dealers request it, but it is not automatic.
For laboratory-grown diamonds, GIA also inscribes a report number along with the text "Laboratory Grown" on the girdle, providing an additional layer of identification.
HRD Antwerp
HRD Antwerp inscribes its report number on diamonds as part of its standard grading service for most report types. The inscription typically includes the HRD logo and report number. HRD's European client base, particularly in Belgium and the surrounding diamond trade centres, has made girdle inscription a routine expectation.
IGI
IGI includes laser inscription on many of its report types. For laboratory-grown diamonds, IGI inscribes the report number along with "LG" (laboratory-grown) as a standard identification measure. Policies may vary by report category and region, so confirm with the issuing office if inscription is important to your purchase.
Other laboratories
Smaller or regional laboratories may or may not offer inscription. If you are considering a diamond graded by a less widely known laboratory, ask specifically whether the report number has been inscribed and verify it under magnification.
How to Read the Inscription
The inscription sits on the girdle — the diamond's thinnest edge. You will not see it with the naked eye. Here is what you need:
Using a jeweller's loupe (10×)
A standard 10× triplet loupe is sufficient to see most inscriptions, though it requires practice and good lighting:
- Hold the diamond with tweezers or a gem holder so the girdle faces you.
- Position the loupe close to your eye and bring the diamond into focus.
- Rotate the stone slowly. The inscription occupies only a small section of the girdle circumference.
- Look for a faintly frosted line of text against the girdle surface. On a polished girdle, the inscription stands out as a matte trace. On a faceted girdle, it may be slightly harder to locate because the facet junctions break up the surface.
Good overhead lighting helps. Tilt the diamond to catch light at an angle that contrasts the inscription against the girdle background.
Using a microscope
A gemological microscope at 20× to 40× magnification makes the inscription easy to read. Most jewellers and gemological offices have one available. If you are purchasing in-store, ask the jeweller to show you the inscription under magnification — a reputable seller will do so without hesitation.
What if the inscription is not visible?
If you cannot find an inscription, consider these possibilities:
- The report type does not include automatic inscription. A GIA full Diamond Grading Report without the optional inscription service will have no girdle marking.
- The diamond has been re-polished. Because the inscription is surface-level, re-cutting or re-polishing the girdle removes it. A re-polished diamond may have a valid report but no matching inscription. In such cases, the diamond should be re-submitted to the laboratory for verification.
- The inscription has worn or been obscured. Heavy wear in a bezel setting, for example, can occasionally affect girdle surface quality over decades — though this is uncommon.
Why Inscription Matters
Matching stone to report
This is the primary purpose. When you buy a diamond, the inscription lets you physically confirm the report belongs to that stone. Without it, you rely on matching measurements and weight — which is possible but less definitive, since multiple diamonds can share similar dimensions. See Report vs Certificate for why the report itself is an assessment, not a guarantee — and matching it to the right stone is your responsibility.
Identification after purchase
Life happens. Diamonds leave their settings for cleaning, repair, resizing, or resetting. An inscribed report number means you can always identify your stone, even outside its mounting. If a diamond is ever separated from its documentation — during an insurance claim, estate settlement, or simple reorganisation — the inscription reconnects stone to paperwork.
Resale and transfer
When selling or passing on a diamond, an inscription provides the next owner with immediate verification. They can look up the report number in the laboratory's online database (see Online Report Verification) and confirm the grades match. A diamond with a verifiable inscription and a matching report is easier to sell and commands greater confidence in the secondary market.
Protection against substitution
In the Czech Republic, as in any market, concerns about stone switching — whether during repair, appraisal, or resale — are legitimate. An inscribed report number is the simplest safeguard. Before handing a diamond to anyone for service, note the inscription number. When you receive it back, verify the number matches under magnification. This takes thirty seconds and eliminates uncertainty.
Summary
The report number is the link between a diamond and its grading documentation. When that number is laser-inscribed on the girdle, the link becomes physical — etched into the stone itself at a scale only magnification reveals. GIA inscribes automatically on Dossiers and optionally on full reports; HRD and IGI include inscription on most report types. Reading the inscription requires a 10× loupe or a microscope, and any reputable jeweller will show it to you on request. Before purchase, verify the match between inscription and report. After purchase, use it to identify your stone during service, insurance, or resale. It is a small marking with outsized practical value. For broader context on how grading reports work, see Reports 101.