GIA vs. IGI: Diamond Certificates Explained

Two laboratories grade nearly every diamond you will be offered. GIA, the Gemological Institute of America, is the non-profit that wrote the 4Cs and the D-to-Z color scale in the 1950s, and its reports are the reference the whole trade measures itself against. IGI, the International Gemological Institute, began in Antwerp in 1975 and today grades the majority of the world’s laboratory-grown diamonds. Here is how they compare, as of this writing.

Natural center stones: GIA. The stones we set are G–H in color and VS2 in clarity, we prefer None or Faint fluorescence, and we buy them against GIA reports inside the Israel Diamond Exchange. On the hand that is a white, clean stone; on paper it is the grade the next buyer will trust.

Laboratory-grown center stones: IGI. D–E color and VVS2–VS1 clarity, at the top of the scale, because at laboratory-grown prices the step from a good grade to the best one is small and we would rather you had it. Every stone comes with its IGI report and the number on the girdle.

Pieces with no single center stone, such as tennis necklaces, tennis bracelets, half-eternity rings and hoops, come with an international jewelry certificate for the finished piece, stating the total diamond weight and quality, since no laboratory grades forty small stones one by one.

How it works in practice. You choose a design and tell us the stone you want; we reply with the reports of the stones we can offer, with their exact measurements, and show them on a video call if you like. You choose. Before the ring is packed we read the inscription under the loupe against the report, and the report travels with the ring. It is yours to keep, for insurance and for the day you might want to reset or sell the stone.

How the stone looks face-up. Two ovals with identical reports can differ completely in the hand: one with a faint bow-tie that flickers and one with a dark bar across its middle. No line on the report records it. The same is true of a cloudy stone whose clouds happen not to be plotted, of a step cut whose inclusion sits exactly under the table, and of a round whose brilliance is merely correct rather than alive.

How it looks on a hand. Size on paper is millimeters; size on a finger is proportion. A 1-carat oval reads as a different ring on a size 4 and a size 8 hand, and the report is silent on both.

What a fancy color is worth. This guide is about white diamonds, graded D to Z. Pink, yellow, blue and the other fancy colors are graded on a separate scale, from Faint through Fancy, Fancy Intense and Fancy Vivid, with a named hue. Here the report reaches its limit fastest: two stones with the identical words on paper, say “Fancy Yellow” and the same clarity, can differ in price several times over, because one has a purer, more saturated hue, an even spread of color across the stone, and a cut that holds it, while the other does not. Nothing on the report records that. A fancy color diamond is bought with the eyes, from a dealer who has it in hand, and the certificate confirms what it is rather than what it is worth.

Whether the price is right. The report names no price, and a strict report on an ordinary stone does not make it a bargain. Compare the price with other stones of the same grades, from the same laboratory, and then look at the stone.

For all three, the answer is the same and it is simple: see the stone, face-up, in daylight, before it is set. We put ours in front of the camera on a video call, and on the bench at the Exchange for anyone passing through Ramat Gan.

We read reports every day, so here is what the paper looks like from our side of the bench, with the caveat that this is our experience and not a survey.

The report is where the conversation starts, not where it ends. Most people who write to us from abroad have read about the 4Cs and arrive with a grade in mind. The useful conversation is nearly always about the lines they have not read yet: the measurements, the fluorescence, the comments, and where on the plot the inclusions sit. Two stones with the same letters, a different answer to each.

The rings that come to us from elsewhere. When a customer brings a ring to be resized or reset, we check the inscription against the paper as a matter of course. Usually it matches. Occasionally the paper is from a laboratory whose grades we would not buy against, and the owner learns, years later, that their “G VS1” is an I SI1 by the scale everyone else uses. That is the single most common disappointment we see, and the easiest to avoid: buy on a GIA or IGI report, and verify it.

The change at GIA. Since October 2025 we have been asked often whether a laboratory-grown stone “should” have a GIA report. The honest answer is that it no longer can, in the sense people mean; the full grades now come from IGI, and that is the paper we send. Natural stones are unchanged, and for those we remain where we have always been, on GIA.