Introduction
Near the top of every diamond grading report, just below the report number and date, you will find a line identifying the stone's shape and cutting style. On a GIA report, this entry might read "Round Brilliant," "Emerald Step Cut," or "Pear Modified Brilliant." It looks straightforward — and it is, once you understand what each term means and why the laboratory records them together.
This line does more than label the diamond. It determines which grading criteria the laboratory applies. GIA assigns an overall cut grade only to standard round brilliants. Every other combination of shape and cutting style receives proportions and finish assessments but no composite cut grade. Understanding what the report means by "shape" and "cutting style" helps you interpret the grades that follow and sets realistic expectations for what information the report will and will not provide.
For a general overview of report layout, see How to Read a Report. For details on the grades themselves, see The 4Cs Panel.
Shape: The Outline
Shape refers to the diamond's face-up outline — the silhouette you see when looking at the stone from above. The most common shapes in the market are round, oval, cushion, emerald (rectangular with cut corners), princess (square), pear, marquise, radiant, and asscher.
Laboratories record the shape exactly as they observe it. A round diamond is "Round." An oval is "Oval." A pear-shaped stone is "Pear." There is no ambiguity in this part of the description — it refers to geometry, not aesthetics.
Shape matters for grading because each outline handles light differently. A round stone distributes light symmetrically across its facets; an elongated marquise concentrates light along its length. The proportions that produce optimal brightness in a round diamond are not the same as those for an emerald cut. By identifying the shape first, the report signals which set of evaluation standards applies.
For detailed guides to individual shapes — recommended proportions, common issues, and what to look for — see the articles in the Shape Guides section.
Cutting Style: The Facet Arrangement
Cutting style describes how the facets are arranged on the diamond's surface. There are three primary cutting styles recognised across all major laboratories:
Brilliant cut
The brilliant cutting style uses triangular and kite-shaped facets radiating outward from the centre of the stone. A standard round brilliant has 57 or 58 facets (58 if a culet facet is present). This arrangement is engineered for maximum light return — brightness, fire, and scintillation. The vast majority of round diamonds on the market are brilliant cuts.
Step cut
The step cutting style uses rectangular facets arranged in parallel rows, like steps on a staircase. The emerald cut is the most recognised step-cut shape. Step cuts produce broad, mirror-like flashes of light rather than the fine sparkle pattern of a brilliant. They emphasise clarity and transparency over raw brilliance, which is why inclusions and colour tend to be more visible in step-cut stones.
Mixed cut
A mixed cutting style combines brilliant-cut and step-cut facet arrangements on the same stone — typically a brilliant-cut crown with a step-cut pavilion, or the reverse. The radiant cut and some modern cushion cuts use mixed faceting. This approach aims to blend the brilliance of triangular facets with the clean lines of step-cut geometry.
What "Modified" Means on a Report
When a grading report reads "Pear Modified Brilliant" or "Marquise Modified Brilliant," the word "modified" has a specific technical meaning. It indicates that the facet arrangement follows the general principle of the named cutting style but departs from the standard pattern.
In GIA terminology, the "standard brilliant" is specifically the 57-facet round brilliant arrangement codified over decades of cutting practice. Any brilliant-style facet pattern applied to a non-round outline is, by definition, modified — the facets have been adapted to fit a different shape. A pear brilliant does not have the same facet count or geometry as a round brilliant, even though both use triangular and kite-shaped facets designed to maximise light return.
The same logic applies to step cuts. An "Emerald Step Cut" uses the classic rectangular-facet arrangement in an emerald (octagonal) outline. If a cutter applies step-cut faceting to an unusual outline or alters the standard facet configuration, the report will note "Modified Step Cut."
"Modified" is not a quality judgement. It does not mean the cutting is inferior or experimental. It simply means the facet pattern has been adapted from the reference standard to suit the diamond's shape. Most fancy-shape diamonds on the market carry the "modified" designation — it is the norm, not the exception.
Common Report Entries
Here are the shape and cutting style descriptions you will encounter most frequently on GIA reports:
- Round Brilliant — the standard 57/58-facet round diamond. The only shape that receives a GIA cut grade.
- Oval Modified Brilliant — an oval outline with brilliant-style faceting adapted to the elongated shape.
- Cushion Modified Brilliant — a square or rectangular outline with rounded corners and brilliant-style facets. Some cushion variants use a "crushed ice" facet pattern that produces smaller, more scattered light reflections.
- Emerald Step Cut — a rectangular outline with cut corners and parallel step-cut facets. Prized for its hall-of-mirrors optical effect.
- Princess Modified Brilliant — a square or near-square outline with brilliant-style faceting. Also referred to as "Square Modified Brilliant" on some reports.
- Pear Modified Brilliant — a teardrop outline with brilliant-style facets.
- Marquise Modified Brilliant — an elongated, pointed-end outline with brilliant-style facets.
- Radiant Modified Brilliant or Cut-Cornered Rectangular Mixed Cut — a rectangular shape with trimmed corners and mixed faceting. Terminology varies between laboratories and report versions.
- Asscher Step Cut or Square Emerald Step Cut — a square outline with step-cut facets and deeply cut corners.
HRD Antwerp and IGI use similar descriptive conventions. Minor differences in wording exist — for instance, HRD may describe a cushion as "Cushion Brilliant" rather than "Cushion Modified Brilliant" — but the underlying classification is the same.
Why This Section Matters for Buyers
The shape and cutting style line serves three practical purposes when you are evaluating a diamond.
It confirms identity. Before reading any grades, verify that the shape described on the report matches the stone in front of you. If the report says "Oval Modified Brilliant" but the diamond is clearly a cushion, you have a mismatch — either the wrong report has been paired with the stone, or the diamond has been re-cut since the report was issued. Either scenario demands clarification. See Report Number & Inscription for how to verify the match.
It sets grading expectations. Only standard round brilliants receive an overall GIA cut grade. If you are buying an oval, emerald, or any other fancy shape, the report will not include a cut grade line. You will need to evaluate the diamond's proportions and finish grades independently. Knowing this in advance prevents confusion. See Cut Grade Scale for which shapes qualify and Proportions Primer for how to assess fancy-shape proportions yourself.
It affects visual character. A "Cushion Modified Brilliant" and a "Cushion Mixed Cut" may both be cushion-shaped, but they handle light differently. The brilliant-cut version will show more traditional sparkle; the mixed-cut version may produce a different balance of brightness and broad flashes. Understanding the cutting style helps you anticipate how the diamond will look in person, beyond what the report's grades alone communicate.
Czech Consumer Note
In the Czech Republic, most diamonds sold with laboratory reports carry GIA, HRD, or IGI documentation. The shape and cutting style field is written in English on all three laboratories' reports, regardless of where the stone is purchased. Czech retailers may translate the shape name in their own product listings — "kulatý briliant" for Round Brilliant, "smaragdový brus" for Emerald Step Cut — but the report itself will always use the English terminology described above. When comparing a retailer's description to the report, match the English terms on the document to confirm consistency.
Under EU consumer protection regulations applicable in the Czech Republic, the product description provided by the seller should accurately reflect the grading report. If a retailer describes a diamond as a "cushion cut" but the report reads "Radiant Modified Brilliant," ask for clarification. The report is the authoritative document.
Summary
Shape and cutting style occupy a single line on a grading report, but that line carries meaningful information. Shape identifies the diamond's outline; cutting style identifies its facet arrangement. Together, they determine which grading criteria the laboratory applies and set your expectations for the grades that follow. The term "modified" signals an adapted facet pattern — standard for any non-round brilliant — and carries no quality implication. Before evaluating any other section of the report, confirm that the shape and cutting style match the diamond you are considering. It is the simplest verification step and the one most often skipped.