What Is a Diamond Laser Inscription

Grading labs and some manufacturers use a fine laser to write characters onto the girdle of a diamond. The characters are only a few microns deep and measure well under 1 mm in height. They do not change the clarity or color grade, because they sit on the surface of the edge, not inside the stone.

Most inscriptions are the report number. Some also include the lab's initials, a brand name, or a phrase. GIA states that every lab-grown diamond it reports on is inscribed with its GIA number and the words "Laboratory-Grown". IGI also inscribes report numbers, and lab-grown stones it grades commonly carry an LG prefix.

The girdle is the narrow band around the widest part of the diamond, where the top (crown) meets the bottom (pavilion). On a mounted ring, it sits just under the prongs. That is why you sometimes need to rotate the ring to find the one spot between prongs where the text shows.

Shape	Where to look
Round	Anywhere around the edge; rotate slowly
Oval, cushion	Often along a long side
Pear, marquise	Along a straight side, away from the points
Emerald, radiant	On a long side of the rectangle
Heart	On one of the curved lobes

1. Clean the stone first; oil on the girdle hides the text.
2. Use a 10x jeweler's loupe and good light from the side.
3. Hold the ring so the girdle faces you edge-on, and tilt it slightly until the light catches the text.
4. Rotate slowly between prongs. The characters look like faint white or gray writing.

It takes practice. Phone macro lenses can work on loose stones. Any jeweler with a microscope can read it in under a minute.

Type the inscribed number into the lab's online lookup: GIA Report Check or IGI's verify page. The online record should match your paper report on carat weight, shape, measurements, color and clarity. If the numbers or the measurements do not match, the stone is not the one on the report.

Our house diamond rings are graded E color and VS1 clarity, such as the Round Lab Diamond Ring 4.62 ct, 14K Yellow Gold ($2,800) and the Cushion Lab Diamond Ring 3.75 ct, 14K Yellow Gold ($3,800). When you look at a ring in the showroom, ask about its grading and look at the girdle under the loupe with us. For what the grades mean, see the diamond clarity chart and what VVS diamonds are.

Lab-grown and natural diamonds are chemically the same, and you cannot tell them apart with a loupe. That is why inscriptions matter for lab stones. The FTC's Jewelry Guides require sellers to disclose clearly that a diamond is lab-grown, and an inscription is a permanent second layer of that disclosure.

• GIA: "Laboratory-Grown" plus the GIA number on lab stones it assesses.
• IGI: report number, commonly with an LG prefix on lab-grown reports.
• Natural stones: report number only, if inscribed at all.

An inscription can be polished off by a cutter, so a missing inscription is not proof of anything. A spectroscopy test at a lab is the only sure way to confirm origin. Compare the two labs in diamond certificates: GIA vs IGI.

	Laser inscription	Grading report	Appraisal
What it is	Text on the diamond itself	Lab document describing the stone	Value estimate for insurance
Who makes it	Lab or manufacturer	GIA, IGI or another lab	An appraiser
What it proves	Which stone matches which report	Carat, color, clarity, cut, origin	Replacement cost on a date
Can it go missing	Can be polished off	Paper can be lost; online record stays	Needs updating every few years

The three work together. The inscription links the stone to the report, the report describes it, and the appraisal puts a dollar figure on it for your insurer. Labs can also inscribe a short personal message, such as a date or initials, next to the report number for a fee.

If your diamond has a report but no inscription, a grading lab can usually add one. The stone normally has to be loose, so a jeweler unsets it, sends it to the lab, and resets it when it comes back. Labs charge a small fee per stone, and some will re-check the grades at the same time. For a center stone worth thousands, this is cheap insurance: it ties the stone to its paperwork for as long as you own it. Ask your jeweler to note the inscription on your appraisal once it is done.

• It ties the stone to the report, so the grades you paid for are the grades you got.
• It helps police and insurers identify a recovered stone after a theft.
• It lets you check that a stone returned from cleaning or a setting job is your stone.
• It tells a future buyer exactly what they are looking at.

Write the inscription number down with your appraisal and keep a photo of the report. Report numbers are covered with the rest of the vocabulary in our jewelry glossary. For carat basics see carat vs karat, total carat weight and the 4Cs guide.