What Triple Excellent Means on an IGI Diamond Certificate and Why It Matters

Triple Excellent on an IGI diamond certificate means a round brilliant diamond has earned the highest possible grade in all three craftsmanship categories: cut, polish, and symmetry. Each grade is assessed independently, and all three must reach Excellent for the designation to apply. A stone with even one grade at Very Good does not qualify, no matter how strong the other two are.

That distinction matters more than it sounds. Cut controls how much light the diamond captures and returns to your eye. Polish controls how cleanly each of the 58 facets transmits that light. Symmetry controls whether every facet is precisely placed so the light exits where the cutter intended. When all three reach Excellent, the stone is performing at its optical ceiling, and you can see it in normal light without any equipment.

What does each grade on an IGI certificate actually measure?

The three grades are related but not interchangeable, and conflating them is the most common mistake buyers make when reading a certificate.

Cut is the most consequential of the three. For round brilliant diamonds, IGI compares the stone’s proportions against its own research on brightness, fire, scintillation, and pattern to assign the grade. An Excellent cut maximizes all three optical phenomena simultaneously: brilliance (white light return), fire (the rainbow dispersion of light), and scintillation (the sparkle pattern when the stone or the viewer moves). Cut is the one C that is entirely human-controlled after the rough stone exists, which is why a well-cut 1.2-carat stone will often look larger and livelier than a poorly cut 1.5-carat stone.

Polish describes the surface smoothness of each facet after the wheel has finished its work. Excellent polish means no polish lines or surface defects are visible under 10x magnification. Think of each facet as a small mirror: the smoother the surface, the cleaner and sharper the reflection. Surface defects, even minor ones invisible to the naked eye, scatter light before it has a chance to perform.

Symmetry is the precision of facet alignment and placement. A grader assessing symmetry checks whether the crown and pavilion are properly aligned at the girdle, whether the table is centered, whether matching facets are identical in shape and angle, and whether the overall outline is true. Excellent symmetry ensures light enters and exits exactly as the cutter intended, without being redirected by misaligned facets.

Critically, if polish or symmetry come in below the level suggested by a stone’s proportions, IGI will pull the overall cut grade down to match. Two stones with the same table percentage and depth can land on different cut grades based on finish quality alone.

Why does Triple Excellent matter specifically for lab grown diamonds?

Lab grown diamonds are physically and optically identical to mined diamonds, so the same grading criteria apply. But there is a practical reason Triple Excellent carries particular weight in the lab grown category.

Because lab grown production has scaled significantly over the past several years, the market now contains a wide range of cutting quality. A grower can produce rough in a controlled environment, but the cutting is still done by hand, and that is still where precision varies. IGI is the most widely accepted certification body for lab grown diamonds, and it applies the full grading scale to every stone it processes. When you see Triple Excellent on an IGI lab grown certificate, you know the cutting team made no compromises on any of the three craftsmanship grades.

The grade spread also matters for price comparison. Two IGI-certified lab grown round brilliants at the same carat weight, color, and clarity can carry noticeably different prices depending on cut quality. A stone graded Excellent/Very Good/Very Good on cut, polish, and symmetry will typically cost less than a 3EX stone, and the optical difference, particularly in fire and scintillation, is often visible in normal indoor lighting.

Does Triple Excellent apply to all diamond shapes?

No, and this is where buyers sometimes get confused. The Triple Excellent designation applies exclusively to round brilliant cut diamonds. Fancy shapes such as ovals, cushions, emeralds, and pears do not receive an overall cut grade from IGI. They are assessed on polish and symmetry only, which means the best a fancy shape can achieve is a “Double Excellent” in those two categories.

This is not a flaw in the grading system. Fancy shapes have no standardized ideal proportions the way round brilliants do, so assigning a single cut grade would be misleading. For fancy shapes, buyers should focus on the individual polish and symmetry grades, along with the stone’s specific measurements, to evaluate light performance.

If you are shopping for a round brilliant and the certificate does not list all three grades, or lists them without specifying the level, ask the retailer to confirm each one individually before purchasing.

Triple Excellent Is the Baseline Worth Holding

For a round brilliant lab grown diamond, Triple Excellent is not a luxury tier. It is the standard that confirms the cutter did not sacrifice optical performance at any stage of the finishing process. Color and clarity grades tell you about the stone’s raw material. Cut, polish, and symmetry tell you what the craftsman did with it.

A diamond graded Excellent across all three will return more light, show more fire, and hold its visual presence across a wider range of lighting conditions than a stone where even one grade slips to Very Good. The premium for Triple Excellent over Very Good grades tends to be modest relative to the total price of the piece, and the optical return is real and consistent.

At Ouros Jewels, every IGI-certified round brilliant starts from that baseline. If you want to see what that looks like in a finished piece, the IGI Certified Round Lab Grown Diamond Solitaire Engagement Ring is a good place to start.

Frequently Asked Questions

Can a lab grown diamond with Triple Excellent grades still look dull in some lighting?

Yes, though it is uncommon. Triple Excellent confirms the cutting meets the highest grading standard, but subtle proportion variations within the Excellent range can still affect how a stone performs in low or diffuse light. Reviewing a video of the specific stone under multiple lighting conditions, alongside the certificate, gives you the most complete picture before buying.

Is IGI Triple Excellent the same standard as GIA Triple Excellent?

No. Both labs grade cut, polish, and symmetry on the same Excellent-to-Poor scale, but GIA’s cut grading is generally considered slightly stricter. A stone with borderline proportions may earn Excellent from IGI but only Very Good from GIA. For lab grown diamonds specifically, IGI is the most widely used and accepted certification body, and its Triple Excellent grade is a meaningful and reliable benchmark.

Does Triple Excellent affect the resale value of a lab grown diamond?

Cut quality does influence resale desirability, and Triple Excellent stones tend to be easier to sell privately or trade in because buyers and appraisers recognize the grade. That said, lab grown diamonds as a category have seen significant price movement since 2020, so resale value is driven more by market conditions than by cut grade alone.

If I am buying a fancy shape like an oval or cushion, what should I look for instead of Triple Excellent?

For fancy shapes, focus on Excellent grades in both polish and symmetry, then examine the stone’s length-to-width ratio and depth percentage for your preferred shape. An oval with Excellent polish and symmetry, a depth between 58 and 62 percent, and a length-to-width ratio near 1.35 to 1.50 will typically perform well, though personal preference for outline shape plays a role too.

Why do some IGI certificates show “Excellent-Ideal” rather than just “Excellent” for cut?

IGI uses “Excellent-Ideal” as its top cut designation for round brilliant diamonds, which is functionally equivalent to what the trade calls Excellent. The hyphenated label reflects IGI’s internal grading language and does not indicate a separate tier above Excellent. If all three grades on the certificate read Excellent or Excellent-Ideal, the stone qualifies as Triple Excellent.