Where the inscription sits
The girdle is the thin edge where the crown (top) and pavilion (bottom) of a cut diamond meet. In a setting it is usually partly covered by prongs or a bezel and not visible from above – the ideal place for a marking that does not affect the stone.
What is engraved
In most cases the laboratory's report number, often preceded by the laboratory code: "GIA 2233908899". On request, laboratories and jewellers also engrave brand names, logos or personal text. The engraving is made with a laser that removes a wafer-thin layer; it is only a few micrometres deep and invisible to the naked eye.
GIA inscribes most of the diamonds it grades; the inscription then appears on the report under "Inscription(s)". IGI also inscribes as a rule; at HRD Antwerp the inscription is optional. A stone without an inscription is therefore not suspicious – but stone and report can then only be matched by measurements, weight and the plotting diagram.
How to read it
With a jeweller's loupe (10×) in good light, hold the stone so the girdle is visible from the side and turn it slowly. The inscription is small and takes some patience the first time; a jeweller or gemmologist finds it in seconds with a microscope. On set stones it can lie under a prong – then only turning or unsetting helps.
What the inscription proves
It shows that this stone is the one the laboratory graded under this number – provided the number matches the laboratory's online record. A paper report can be copied or placed with another stone; the engraving in the diamond cannot be without leaving traces. That is why every check includes: look the number up online (GIA Report Check, IGI Verify, HRD Antwerp), read the inscription, compare the measurements.
What it does not prove
An inscription says nothing about quality or origin; the report and the origin documentation do that. In theory an inscription can be polished off (the stone then loses weight and would have to be regraded) or a false number engraved later – which is why matching against the online database and the measurements remains indispensable. An inscription alone, without a check with the laboratory, is just a number on the stone.
Technique and history
Laser inscriptions on diamonds have existed since the 1980s; GIA has offered them as part of grading since the late 1990s. Lasers with very short pulses are used that remove a layer of a few micrometres from the girdle without heating or weakening the stone. The characters are typically 0.1 to 0.2 millimetres high. The weight of the stone does not change measurably through the inscription; it has no effect on the clarity grade, because inscriptions are excluded from clarity grading and listed separately on the report as Inscription.
Having an inscription made later
Anyone who owns a stone without an inscription can have one made by a laboratory or a specialised jeweller – with the report number or a personal text. Laboratories as a rule engrave the report number only in connection with a grading, so that number and stone verifiably belong together. Set stones usually have to be unset so the girdle is accessible.
Checklist: verifying an inscription
- Note the report number from the stone's page or the report.
- Look the number up online with the laboratory (GIA Report Check, IGI Verify, HRD Antwerp) and compare the data.
- Check on the report whether an inscription is listed and which.
- Search the girdle with a 10× loupe or microscope and compare the inscription with the report.
- Re-measure the dimensions with callipers or at a jeweller.
- In case of discrepancies: ask the dealer, decide before the withdrawal period ends.
Other kinds of inscriptions
Besides the report number, other engravings occur. Makers of branded cuts engrave their logo or brand name, some producers a serial number of their origin programme by which the stone can be traced back to the mine. Jewellers offer personal inscriptions – initials, a date. All these engravings appear on the report under Inscription if they were present at the time of grading; ones added later do not. An inscription the report does not mention is therefore not automatically a problem, but it should be explicable. Conversely, a brand inscription does not replace a report number, because it is not held in a publicly verifiable database.
Inscription and report in our shop
On our stone pages the report number appears next to the laboratory code and is linked to the laboratory's verification service. Whether the stone carries an inscription is stated on the original report enclosed with every delivery. After receipt you can read the inscription yourself or have a jeweller read it – within the statutory withdrawal period for consumers in the EU.