Laser inscription

The girdle is the narrow band around the widest part of a polished diamond, where the top (crown) meets the bottom (pavilion). A laser can etch a short line of text and digits into that band. The marks are invisible to the naked eye and can be read at 10x magnification, the standard power of a jeweller's loupe.

The point is identification. A diamond grading report describes one stone, and the inscription ties that stone to its report number so you can match the two. It is not decoration, and it does not change the diamond's grades.

That depends on the laboratory and the type of stone. For natural diamonds, GIA lists the report number as laser inscribed for its Diamond Dossier, Diamond Focus Report and Diamond Origin Report. GIA's pages for the Diamond Grading Report do not list an inscription, though a GIA grading report has an inscription line that records any text, symbols, logos or report number on the girdle. GIA inscribes every lab-grown diamond it evaluates with the words Laboratory-Grown and a GIA number. Other laboratories, IGI among them, follow their own practice, so read the wording on the report.

You need a 10x loupe and steady light. A jeweller can usually do this with you.

1. Hold the stone in tweezers, or ask the jeweller to hold it, with the girdle facing you.
2. Bring the loupe close to your eye, then bring the stone to the loupe until the girdle edge is sharp.
3. Tilt the stone slowly and change the angle of the light until the marks show up.
4. Read the digits and any wording, and write them down.
5. Compare them with the report number, then check that number on the lab's own website.

The lettering is very small, so expect it to take some patience the first time. If you cannot find it, that is not proof that something is wrong. Ask the jeweller to point it out.

A matching inscription is a strong check that the stone in your hand is the stone the report describes. Look up the number with the lab, and compare shape, carat weight, colour, clarity and measurements. GIA's Report Check, for example, lets you confirm that a report matches what is archived in GIA's database, and you can expect it to ask for the report number and carat weight.

It cannot tell you whether the grades are right for you, whether the price is fair, or how the diamond will look in a setting. Not every diamond is inscribed, and prongs or a bezel in a finished ring may cover part of the girdle. If there is no inscription, ask for the report number in writing and check it with the lab.

An inscription is also not the same as engraving on a band. Band engraving is done on the metal by the jeweller, usually to carry a name, a date or a short message, and it has no connection to the lab report.