If you have spent any time reading about round brilliant diamonds, you have likely encountered the cut grade — GIA's single most useful quality indicator. It distils a complex set of proportions, light-handling characteristics, and finishing details into one word: Excellent, Very Good, Good, Fair, or Poor.
Then you look at an oval or a cushion on a GIA report, and the cut grade is simply not there.
This is not an oversight. It is a fundamental difference in how the industry grades fancy shapes, and understanding it will make you a significantly better buyer.
Why Fancy Shapes Don't Receive a GIA Cut Grade
GIA introduced its cut grading system for round brilliant diamonds in 2006 after more than fifteen years of research. The round brilliant lends itself to systematic grading because its geometry is standardised — 57 or 58 facets arranged in a predictable pattern, with well-defined relationships between crown angle, pavilion angle, table size, and total depth. GIA was able to model millions of proportion combinations and map them to measurable light performance outcomes.
Fancy shapes — ovals, cushions, pears, marquises, emeralds, radiants, princesses, and the rest — do not share that uniformity. An oval can have a narrow, elongated outline or a nearly round one. An emerald cut can carry a steep crown or a shallow one. A cushion can have two rows of pavilion facets or four. The range of acceptable geometries is far wider, and the relationship between proportions and beauty is far less predictable.
GIA has not found a way to reduce that complexity into a single, reliable grade. So instead, GIA reports for fancy shapes include polish and symmetry grades but leave the overall cut assessment to the buyer.
What GIA Does Report for Fancy Shapes
Every GIA grading report — whether for a round or a fancy shape — includes:
- Colour grade (D–Z scale, or the Fancy Colour scale for saturated hues)
- Clarity grade (Flawless to Included, based on the same criteria as rounds)
- Carat weight
- Polish grade (Excellent to Poor) — the quality of the surface finish on each facet
- Symmetry grade (Excellent to Poor) — how precisely the facets align with one another and how balanced the overall shape is
- Fluorescence (None to Very Strong)
- Proportions — measurements including depth percentage, table percentage, and the length-to-width ratio
What is absent is the overall cut grade line. Polish and symmetry are components of cut, but they do not tell you how well the diamond handles light. A fancy shape can have Excellent polish and Excellent symmetry and still be poorly proportioned — deep enough to face up small, or shallow enough to leak light through the pavilion.
AGS: The Exception
The American Gem Society (AGS) does assign cut grades to certain fancy shapes. AGS developed its own light-performance-based grading system — the AGS Performance Cut Grade — which uses ray-tracing software to measure how effectively a diamond returns light to the viewer. This system has been applied to princess cuts, ovals, cushions, and emerald cuts, among others.
An AGS Ideal (0) cut grade on a fancy shape is a meaningful indicator of light performance. However, AGS-graded fancy shapes represent a small fraction of the market. Most fancy-shape diamonds you encounter will carry GIA reports without a cut grade, and you will need other tools to evaluate their cutting quality.
How to Evaluate Fancy-Shape Cutting Quality
Without a cut grade to guide you, assessing a fancy shape requires looking at several factors together. None of them alone tells the full story, but in combination they give you a reliable picture.
Symmetry of Outline
The silhouette matters. An oval should have two halves that mirror each other along both its length and width axes. A pear should have a smooth, balanced curve on each side of its point. A heart shape should have matched lobes. Outline asymmetry is visible to the naked eye and affects how the diamond looks in its setting.
GIA's symmetry grade captures some of this, but it primarily evaluates facet alignment rather than the overall shape outline. Your own eyes are a good judge here — if the shape looks uneven, trust that instinct.
Depth and Table Percentages
These are the two most accessible proportion numbers on any grading report, and they serve as useful starting filters.
Depth percentage is the total depth of the diamond divided by its average width. A diamond that is too deep carries hidden weight in its pavilion — you pay for carats you cannot see face-up. Too shallow, and light leaks through the bottom instead of returning to your eye.
Table percentage is the width of the top facet relative to the overall width. A very large table can reduce fire (the spectral colour flashes you see when a diamond moves), while a very small table limits brightness.
Each shape has its own range of preferred proportions. What works for an emerald cut does not work for a marquise. The proportions that produce the best light performance in one shape may produce windowing or extinction in another.
Learn about ideal proportions for each shape →
The Window and Extinction Test
These are the two most common cutting flaws in fancy shapes, and they are visible if you know what to look for.
Windowing occurs when light passes straight through the diamond without reflecting back. You see through the stone as if looking through glass — often visible as a pale, washed-out area in the centre. Windowing typically results from a pavilion that is too shallow.
Extinction is the opposite problem: areas of the diamond that appear dark, even under good lighting. Some extinction is normal — no diamond returns light from every angle at once. But excessive or poorly distributed extinction makes a stone look lifeless. Fancy shapes are particularly prone to extinction in their corners and ends.
The Bow-Tie Effect
Elongated fancy shapes — ovals, marquises, and pears — almost always display a bow-tie pattern: a dark area across the width of the stone, shaped like a bow tie. A faint bow tie is normal and not a flaw. A prominent, distracting bow tie indicates proportions that create a persistent zone of light leakage, and it detracts from the diamond's beauty.
The severity of a bow tie cannot be determined from a grading report. It must be evaluated visually, either in person or through high-quality imagery.
Read more about the bow-tie effect →
Advanced Imaging: Substituting for the Missing Cut Grade
For buyers who want objective data on a fancy shape's light performance, two tools developed for the trade can fill the gap left by the absent cut grade.
ASET (Angular Spectrum Evaluation Tool)
Developed by AGS, the ASET map shows how a diamond gathers light from different angles. It uses three colours:
- Red represents light gathered from steep angles — the primary source of brilliance
- Green represents light from lower angles — contributes to brightness but less intensely
- Blue represents light blocked by the observer's head — creates contrast, which is desirable in moderation
- White or black areas represent light leakage — this is what you want to minimise
A well-cut fancy shape will show a predominantly red ASET image with balanced contrast and minimal leakage.
IdealScope
The IdealScope uses a simpler colour scheme — red for returned light, white for leakage, and black for contrast. It is a quick, accessible way to identify light leakage in any diamond. For fancy shapes where no cut grade exists, an IdealScope image immediately reveals whether the stone is returning light effectively or losing it through the pavilion.
Many reputable online diamond vendors now provide ASET or IdealScope images alongside their standard photography, precisely because these tools answer the question that the grading report leaves open for fancy shapes.
Summary
- GIA does not assign a cut grade to fancy-shape diamonds. Only round brilliants receive one. This is because fancy shapes vary too widely in geometry for a single grading scale.
- AGS does grade some fancy shapes using ray-tracing-based light performance analysis. An AGS Ideal grade on a fancy shape is a reliable quality indicator.
- Polish and symmetry are not substitutes for a cut grade. They evaluate surface quality and facet alignment, not how well the diamond handles light.
- Evaluate fancy shapes using multiple factors: outline symmetry, depth and table percentages, windowing, extinction, and bow-tie severity.
- Each shape has different ideal proportions. Do not apply round-brilliant rules to fancy shapes.
- ASET and IdealScope imaging can objectively reveal a fancy shape's light performance where the grading report cannot.
- See the diamond — or see its images. With no cut grade to rely on, visual evaluation (in person or through advanced imaging) is essential for fancy shapes.
Frequently Asked Questions
Why doesn't GIA grade fancy-shape diamond cut quality?
GIA's cut grading system was designed for round brilliants, which have standardised geometry. Fancy shapes vary too widely in acceptable outlines, facet counts, and proportion relationships for a single grade to be reliable. GIA reports polish and symmetry but leaves the overall cut assessment to the buyer.
How do I evaluate a fancy-shape diamond without a cut grade?
Assess four factors together: outline symmetry (the silhouette should look balanced), depth and table percentages (within the preferred range for the shape), windowing and extinction (light leakage or dead zones), and bow-tie severity (for elongated shapes). ASET and IdealScope images provide objective light-performance data.
Is an AGS cut grade on a fancy shape reliable?
Yes. AGS uses ray-tracing software to measure how effectively a diamond returns light, and an AGS Ideal (0) grade on a fancy shape is a meaningful indicator of cutting quality. However, AGS-graded fancy shapes represent a small fraction of the market.
Can a fancy-shape diamond have Excellent symmetry but poor light performance?
Yes. GIA's symmetry grade evaluates facet alignment, not how well the diamond handles light. A fancy shape can receive Excellent polish and Excellent symmetry while being poorly proportioned — too deep, too shallow, or carrying a severe bow-tie.