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Diamond cut grading standards


It may surprise you to learn that nearly 70% of round diamonds have the GIA Excellent cut grade.

That seems out of line with D color and Flawless clarity

It is. Color and clarity have been strictly graded since the 1930s but the world's largest laboratory, GIA, has only graded cut since 2006. The American Gem Society started in 1996, but revised their system several times. In fact, since 1980 the world’s major grading labs have launched, revised and re-introduced various systems over a dozen times, with no uniform approach. Some use arbitrary systems, others use repeatable science. The one thing they have in common is a far softer approach to judging cut-quality than to grading the natural Cs of color and clarity.

Our philosophy

We absolutely love diamonds. Mother nature took millions of years to shape, cook and deliver these hardest of natural wonders to us. Man cuts and polishes her gifts to their finished state. The diamond trade imposes strict standards on mother nature when grading her colors and clarities. At High Performance Diamonds we believe cut quality should be held to such standards too.

Cut is king

If you read our short Diamond 101 you already know that cut quality influences diamond beauty more than any other C. Diamond professionals all know this, yet we encounter shoppers who are unaware that labs all have their own approaches to this C. They're also unaware that cut grading is rather permissive and wide.

So, how wide are cut grades?

For perspective, compare cut grades to those long-established color and clarity grades. Even trained gemologists have difficulty separating D-E-F color outside a lab, especially when mounted. And it's impossible to separate Flawless, VVS1, VVS2, VS1 and VS2 clarity grades without magnification. Yet anyone can see clear quality differences between different diamonds with the Excellent or even the Ideal cut grade.

What's being grading?

Simply put; brightness vesus darkness. The GIA compares several averaged measurements to sampled human observations. The AGSL uses scientific computer modeling to score repeatable values for brightness, contrast and leakage.

What's not being graded?

Neither fire nor sparkle. At present no major laboratory performs an actual measurement of dispersion (seen as fire) or scintillation (seen as sparkle), even though many people would say these are the most important and attractive components of diamond performance.

Cut grading standards overview

Graphic data last updated June 10, 2017: 918,330 diamonds total

* In a survey of all GIA graded round brilliant diamonds for sale on the world's largest wholesale platform, over half are graded GIA Triple Excellent (3X) and nearly 70% are Excellent. Some sellers promote the value and rarity of GIA EX to the value and rarity of D color or Flawless clarity because they don't realize how wide and common the EX cut grade actually is.

Hypothetical comparison

From a percentage standpoint, if GIA were to treat color grading like cut grading, all diamonds DEFGHIJKLMNO would receive Excellent in color. PQRSTUV would get Very Good and only WXYZ would be Good, Fair or Poor.

Is this why pricing is so variable?

Yes. A GIA 3X can land anywhere between AGS 0 and AGS 5 in performance (the AGS metric is stricter). By the numbers; most GIA 3X are candidates for AGS 2,3 or 4 in performance. To deduce where a given EX actually falls requires details of spread, proportions and angles. But facet-group data is averaged and further rounded up or down, so definitive predictions aren't possible. Moreover, no measure or analysis of 3D cut precision is provided.

Why would most EX receive lower grades at AGSL?

Economics: Targeting the minimum threshhold for EX allows factories to keep more carat weight in diamonds they produce. This is because the GIA EX range allows steeper combinations that would be penalized for brightness reductions in the AGS system.

What about AGSL?

We applaud AGSL. Their Ideal grade is much stricter than GIA Excellent, which is why fewer diamonds are sent there for grading. Using the color comparison, AGS Ideal would come closer to grading all diamonds DEFG as Ideal in color. That lines up better with human vision, where the differences exist but are subtle. Even so, we should say that AGSL's approach to cut isn't as strict as their color and clarity grading, as you can see differences between diamonds with the AGS Ideal cut grade.

The status quo

Without dispute, the global diamond trade places higher value on diamonds produced with higher levels of 3D cut-precision. But USA laboratories do not grade 3D cut-precision, or even the simple 2D "Hearts & Arrows" patterns one sees in photos. This is a result of long-standing pressure from DTC Sightholders producing millions of carats for sale in the USA - over half of which can remain in the “top grade” of GIA Excellent as long as no stricter components are enforced.

Future value

There is no doubt that cut standards will continue to increase over time. This process is happening right now: Crafted by Infinity personnel are regularly consulted by some of the world's major laboratories on cut-grade improvement. As time passes change will occur; many commercial diamonds will lose value when re-graded by stricter standards, as surely as if D color were suddenly subdivided into multiple grades tomorrow. This affects consumers more than professionals, since the trade already recognizes crafting details which move a diamond's value up or down behind industry doors.

We are on your side

All of the above lends gravity to why our company can extend the superior lifetime return and unrestricted lifetime upgrade policies we do, while companies selling diamonds that don't measure up to Crafted by Infinity can extend no such policies or place time limits or restrictions on what they offer.

Crafted by Infinity Diamonds

Crafted for better brightness, more fire, more sparkle and more life, Infinity Diamonds are fashioned with the future in mind. They go beyond the highest performance marks in all systems, exceeding known metrics, and have done so since 2001, when Paul Slegers began crafting them with his singular vision.

Some of the world’s top optical scientists, appraisers and laboratory facilitators choose to wear Infinity Diamonds themselves, or for their loved ones, acknowledging that Infinity's standards outpace all current metrics and more robust future systems, currently in-research. We celebrate their choice and support of our vision.

Spending your money on Crafted by Infinity is a worthy investment in the planning and cutting expertise, extra time, extra passion and everlasting value of the product. Like any other purchase of elite quality, one may expect to pay slightly more now for a product that will prove itself over and over, to the delight of its owner and heirs, as the years pass.

Information is power

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