How to Judge Fancy-Shape Diamond Cut: Choosing a Diamond Without a Cut Grade
Updated: 5 days ago
When choosing a round brilliant diamond, the cut grade is a useful first filter. Starting with well-graded stones, then comparing their appearance, narrows the search and reduces the risk of selecting a diamond with disappointing optical performance on carat weight, colour and clarity alone. Diamonds within the same good grade can still look different; the grade provides an informed starting point.
With an oval, pear, emerald or cushion shape, an overall cut grade may be absent from the report. Without that first filter, how can you tell whether a diamond is well cut and will sparkle when worn? We recommend first understanding what the report assesses, then examining the outline, proportions, face-up light return and appearance in motion. This approach applies to natural and lab-grown diamonds. Our focus here is on colourless to near-colourless fancy shapes.
Contents
1 Why fancy-shape cut grading is harder to establish
Diamond cutting has a long history, but a repeatable, comparable grading system must establish which visible differences should affect a grade and how to measure them under consistent conditions. The challenge with fancy shapes is that a single shape can accommodate many different cutting designs.
Two ovals can have very different facets and outlines
The basic round brilliant design is relatively consistent. Fancy shapes can vary in length-to-width ratio, shoulder curvature, tips, pavilion facets and facet arrangement. Even two stones with similar table and total depth percentages can send light along different internal paths, producing different patterns of brightness and darkness. An emerald-shaped step cut also requires a different visual approach from an oval brilliant.
Good cut considers both light return and the patterns we see
A diamond may display broad flashes or a fine crushed-ice appearance. Whether a dark area creates attractive contrast or makes the centre look lifeless depends on its position, extent and behaviour as the stone moves. GIA’s 2024 observer study of fancy shapes found a general dislike of obvious windowing, but greater variation in preferences for bow ties, crushed-ice patterns and some outlines. [1]
Fancy-shape grading therefore needs to connect measurable geometry and optical performance with the reasonable visual character of different designs. GIA’s 2026 discussion of cut research includes three-dimensional scanning, ray tracing and analysis under different movements and viewing conditions. [2] This helps explain why a table of table and total depth percentages cannot replace a complete assessment.
2 Read the report: some fancy shapes have a grade, others do not
It is no longer accurate to say that fancy shapes never receive a cut grade. GIA and IGI offer different services, and some diamonds may carry an additional optical assessment. Always check the actual report for the stone you are considering.
Report or assessment | Fancy-shape coverage | How to use it |
Standard GIA grading report | Currently does not provide an overall cut grade for fancy shapes; polish and symmetry information remains available. [3] | Use the workmanship and measurements, then inspect the stone or clear moving images. |
IGI fancy-shape cut grading | An optional overall cut assessment, with grades from Excellent to Poor. [4] | Check whether an overall cut grade is present. Where supplied, use it as screening evidence. |
GIA’s AGS Ideal supplemental report | Eligible shapes, facet designs and qualifying stones can receive an additional assessment. Those meeting the criteria receive AGS Ideal 0. [5] | Use as additional optical evidence. It does not cover every fancy design or mean that ordinary GIA reports grade all fancy-shape cuts. |
What does IGI’s Excellent grade assess?
IGI introduced fancy-shape cut grading in 2022. [6] Its current method has four parts: polish and symmetry, proportion qualification, shape-specific craftsmanship requirements, and light return assessment. IGI explicitly states that proportions alone cannot determine a fancy-shape cut grade. The final light return step assesses overall returning light; it is not a complete analysis of fire or scintillation. [7]
Excellent is therefore valuable screening information, but two Excellent ovals can still show different contrast patterns and flash styles. If an overall cut grade is absent, first establish the report type, service scope and issue date, then arrange a comparison of the stones.
What do Excellent polish and symmetry each mean?
Polish assesses the finish of facet surfaces. Symmetry assesses workmanship such as the outline and facet arrangement. Strong results in both support cut quality, but do not mean that overall light return, fire and scintillation have all received the highest assessment. When you see two Excellent grades, check which fields they belong to. [3]
For Ideal, Excellent, 3EX and hearts and arrows in round diamonds, see our Diamond Cut Grades Explained guide.
3 Use the report for an initial selection without a cut grade
A report remains useful without an overall grade. Its measurements and craftsmanship information help identify points worth investigating. At this stage, the aim is to decide which stones merit a closer look, rather than declaring one the most brilliant from a few percentages.
Report information | What to look for | What to confirm next |
Polish and symmetry | Any significant compromises in workmanship. | Whether outline balance, facet finish or edge finishing affects appearance. |
Length, width, depth and L/W ratio | A broader or more elongated shape; whether face-up dimensions meet expectations. | A balanced outline, shoulders and tips, with proportions suited to the wearer. |
Table and total depth percentages | Proportion combinations that merit closer investigation. | Large dark areas, windowing or uneven light return face-up and on slight movement. |
Girdle and pointed corners | Very thin areas or positions needing extra protection. | Whether the setting protects tips on pears, marquises, princess cuts and similar designs. |
For example, an oval measuring 10.0 × 7.0 mm has a length-to-width ratio of approximately 1.43. Another measuring 10.0 × 6.5 mm has a ratio of approximately 1.54. These figures describe the second stone as more elongated; they do not establish which returns light better. This is a proportion calculation, rather than a grading of two particular diamonds.
Equal carat weight does not guarantee equal face-up size either. Compare millimetre measurements alongside depth, outline and actual optical performance. The desire for a larger face-up appearance should be considered together with cut, durability and the jewellery design.
If using IGI’s shape guidelines to screen candidates, read them together with its craftsmanship requirements and light return assessment. Falling within a proportion range satisfies only part of the criteria. [7] We do not treat an online “ideal range” as a universal pass mark shared by every laboratory and every fancy-cut design.
4 Four things to observe in the actual diamond
After screening the report, examine how light actually appears in the stone. Clean the diamond, begin face-up, then slowly tilt it from side to side and forwards and backwards. The first illustration shows scintillation: the same region changes from dark to bright, or bright to dark, as the angle changes. Then examine the central dark band, windowing, brightness distribution and flash style in turn.
The central bow tie: does it brighten as the stone moves?
Elongated brilliant shapes such as ovals, pears and marquises may display a bow-tie-shaped dark band across the centre. This relates to how their facets show directions where the observer blocks light. Viewing distance, lighting and camera equipment also affect how conspicuous it appears. [9]
We look at whether the band is too broad, whether it dominates the whole stone, and whether bright flashes return to the centre with a slight movement. Some central contrast alternates with light as the stone moves, adding depth to its appearance. If the centre remains a heavy dark band through several everyday viewing angles, a side-by-side comparison with other candidates is worthwhile.
Windowing and leakage: look for large transparent or dull areas
Windowing is a face-up region that acts like a window, allowing the background beneath to show through. Light leakage more broadly describes light that does not return towards the viewer; the affected area may look dull. [2] Consider the extent, position and usual viewing angles, particularly whether a large empty-looking area persists in the centre.
In emerald and Asscher step cuts, observe the alternating reflections in the centre and successive long facet regions. Local transparency on tilting has a different effect on the worn appearance from a large, obvious face-up window. Also distinguish a dark reflection of the surroundings from an area that genuinely reveals the background.
Brightness distribution: do the centre and ends work together?
Start with the life of the whole stone, then examine its centre, ends and edges. Watch for one bright end paired with another that stays grey, or a sparkling centre surrounded by persistently dull areas. Successive areas lighting up during movement are more relevant to wearing a diamond than every facet being bright at the same instant.
Scintillation needs changing contrast: darkness makes the bright flashes more distinct. GIA’s research also emphasises that perceived beauty depends on dynamic contrast patterns as well as the amount of returning light. [2] We look for persistent, unbalanced dark areas while retaining the normal contrast that makes the whole diamond lively.
Flash style: broad flashes and fine crushed-ice patterns
Cushions, radiants and some other fancy designs may display broad areas of light and dark, or dense, fine flashes. Many small visible patterns arise from virtual facets created by repeated internal reflections. They do not necessarily correspond one-for-one to small physical facets. [1]
First establish overall light return and liveliness, then consider whether you prefer distinct broad flashes or a finer rhythm of sparkle. We separate a different visual style from weak optical performance: crushed ice can be lively, while a broad-facet pattern can look dull if large regions remain dark.
Each shape also has its own features to inspect. Look for smooth shoulders in an oval, balanced sides in a pear, coordinated tips and central axis in a marquise, and the arrangement and rhythm of long reflections in step cuts. These shape characteristics affect both the diamond’s appearance and its setting requirements. [8]
Explore our Oval Diamond Buying Guide and Emerald Cut Diamond Buying Guide for more detail on individual shapes.
5 How we approach fancy-shape selection at RAGAZZA
We value the professional evidence that grading provides. An overall cut grade or additional optical report should be put to use. When neither is available, more evidence of the actual stone is needed. We look for a balanced outline, lively light return and no conspicuous problems that undermine the overall appearance at principal viewing angles, together with proportions suited to the jewellery and how it will be worn.
Compare under matching lighting and viewing conditions
For a practical comparison, we recommend viewing under at least soft, diffuse light and point-source lighting. Diffuse light helps reveal the overall distribution of contrast, while point sources help show flashes and fire. Compare candidates in the same environment, at similar distances and angles, rather than judging one under jewellery spotlights and another in a dim room.
Begin with a still face-up view, move slowly from side to side and forwards and backwards, then return face-up. This helps distinguish a temporary dark area from one that frequently dominates. Also view from a normal wearing distance to appreciate the outline and overall sparkle, rather than relying entirely on magnification. This is our suggested comparison method, not a laboratory grading procedure.
Online selection needs continuous views of the same stone
If an in-person viewing is not possible, request clear images that correspond to the actual diamond, ideally including face-up views and a continuous video of slow movement. Ask about the lighting. One carefully selected sparkling photograph cannot explain the central band, light return at the ends and changes across angles. Check videos for overexposure that conceals darkness and detail.
Optical images such as ASET can add information about light return and obstruction when reliably captured, but they need correct interpretation alongside the diamond’s dynamic appearance. [2] We do not force different fancy cuts into a single visual standard based on one colour-distribution image.
Natural or laboratory origin does not remove the need for these cut assessments. A fancy-shape lab-grown diamond should be judged as an individual stone too. We want the diamonds we provide to bring shape and brilliance to the finished jewellery, with the report and visible appearance supporting one another.
6 Frequently asked questions
Q: Is a fancy-shape diamond without a cut grade worth considering?
A: Yes. First establish whether that report type offers the assessment. Then consider craftsmanship, proportions, clear video or an in-person viewing. An absent overall grade means you need further evidence for selection; it does not establish whether the cut is good or poor.
Q: Why inspect the stone if polish and symmetry are both Excellent?
A: These fields primarily describe workmanship. They do not fully describe face-up contrast, the central bow tie or flashes in motion. They are useful screening information; examining the diamond helps confirm its final appearance.
Q: What should I check if IGI has already graded the cut Excellent?
A: Check whether the outline, proportions and flash style suit you, and how the centre, ends and edges perform at everyday viewing angles. IGI’s fancy-shape grading includes light return, but that step is not a full analysis of fire and scintillation. Diamonds within the same grade can still differ in appearance.
Q: Should a visible bow tie rule out a diamond?
A: Consider the band’s size, position and persistence. If it alternates naturally with light as the stone moves, it may be part of the overall contrast. A broad, heavy band across several usual angles merits comparison with alternatives. One photograph is not enough to decide.
Q: Will two fancy shapes with identical table and depth percentages look the same?
A: Not necessarily. Length-to-width ratio, outline, crown and pavilion angles, and facet arrangement can still differ. These geometric differences influence light paths and contrast patterns, so stones with similar percentages still need individual inspection or reliable imagery.
Sources
Grading service information checked on 29 October 2026. For an individual diamond, refer to its report and the applicable service conditions.
