When we talk about diamond cut, we’re not referring to the shape, like round or oval, but to the precision and artistry with which a diamond is faceted. Cut is what determines how a diamond interacts with light, and it’s the difference between a diamond that sparkles and one that sits flat [1].
What Is Diamond Cut? (And What It’s Not)
Let’s clear up one of the most common misunderstandings in the diamond world: cut is not shape.
Diamond Cut vs Diamond Shape
-
Diamond shape refers to the silhouette or outline, think round, emerald, pear, or oval [2].
-
Diamond cut refers to the proportions, angles, symmetry, and polish of a diamond. It’s all about how well the stone has been crafted to reflect and refract light.
A round brilliant diamond, for instance, is designed to maximize sparkle. But if its angles are too steep or shallow, even the most beautiful rough can look dull. On the flip side, a well-cut diamond, regardless of size, catches the light in a way that’s nothing short of magical.
So what does cut impact?
-
Brilliance: the white light that reflects from the surface and inside.
-
Fire: those rainbow flashes you catch in the light.
-
Scintillation: the sparkle that dances as the diamond moves.
Even the most flawless diamond can appear lifeless if the cut isn’t precise.
Why Diamond Cut Matters More Than You Think
Diamond cut does more than define how a stone is shaped, it sets the stage for how a diamond performs in the light [1]. The most finely cut stones appear brighter, livelier, and even larger than their actual carat weight. Their edges catch the eye, and their centers glow with depth.
You may not know all the technical specs when you first look at a diamond, but your eye naturally favors one that’s well-cut. That flash of rainbow fire, that sharp twinkle when it moves, those aren’t accidental. They’re the result of precise angles and proportions working in harmony with light.
Cut influences everything from how a diamond catches daylight to how it sparkles under candlelight. In fact, two diamonds with identical carat and clarity can look dramatically different side by side, just because one was cut with more care.
Diamond Cut Grades Explained
To help make sense of cut quality, the Gemological Institute of America (GIA) developed a grading scale that evaluates how well a diamond reflects light. These grades are based on multiple factors, proportions, symmetry, and polish, and apply most commonly to round brilliant cuts [3].
The GIA Cut Scale:
When you’re looking at a diamond’s grading report, the cut grade offers a quick snapshot of how much light the stone is likely to return.
-
Excellent: Reflects nearly all the light that enters, creating exceptional brilliance. Proportions are balanced and symmetrical.
-
Very Good: Reflects most light, with only minor differences in sparkle. Often indistinguishable from Excellent in casual viewing.
-
Good: Still offers brightness, but may appear less lively under certain lighting due to slightly off proportions.
-
Fair: Allows a noticeable amount of light to escape from the sides or bottom, reducing sparkle.
-
Poor: Most light leaks out, resulting in a dull appearance.
Even within each category, there’s nuance. Subtle shifts in angle or depth can dramatically change a diamond’s performance. That’s why experienced jewelers and gemologists go beyond the grade to assess how a diamond actually looks in person.
Ideal Proportions for Brilliance
Cut grades are a helpful starting point, but what actually makes a diamond brilliant comes down to proportion. These precise measurements, angles, percentages, and facet relationships are what allow a diamond to reflect light beautifully, without losing it through the sides or bottom.
A well-proportioned diamond has a symmetry and balance that gives it life. Too shallow or too deep, and the light escapes, leaving the diamond looking dark or glassy. With the right proportions, the light bounces through the stone and returns to the eye in a bright, clean flash.
Key Elements of a Well-Cut Diamond:
-
Table size: Ideally between 54% and 57% of the diamond’s width. Too large, and you lose fire. Too small, and the stone can look dark.
-
Depth percentage: Should fall between 59% and 62.5%. This affects how much light enters and reflects back.
-
Crown and pavilion angles: These must be in harmony, when one increases, the other often needs to decrease to maintain balance.
-
Girdle thickness: Should be thin to slightly thick. Too thin can make the diamond fragile; too thick can trap light.
-
Culet: Ideally none or very small. A large culet can appear as a dark spot in the center of the diamond.
These values are especially important for round brilliants, but the concept of proportion matters across all shapes. Understanding how these elements interact helps explain why two diamonds with the same carat weight can look completely different in person.
Popular Diamond Cuts (Not to Be Confused with Shapes)
While “cut” often gets mixed up with “shape,” they’re not the same, and both play a role in a diamond’s visual impact. Cut refers to how the diamond is faceted to reflect light, while shape is its outline or form. The style of cut affects sparkle, but the shape influences the overall vibe: soft and romantic, bold and architectural, or clean and classic.
Types of Diamond Cuts
Brilliant Cut
The most popular and sparkly, especially in round diamonds. Features triangular facets that radiate from the center like a starburst, maximizing brightness and fire.
Step Cut
Found in emerald and Asscher shapes. These cuts feature long, rectangular facets that create a mirror-like effect and a subtle, elegant shine rather than intense sparkle.
Mixed Cut
Combines elements of both brilliant and step cuts. Oval, cushion, and radiant shapes often use this hybrid approach to balance sparkle with structure.
Each cut style creates a different type of brilliance and carries its own personality. A step cut may appeal to someone drawn to clean lines and understated elegance, while a brilliant cut suits those looking for maximum dazzle.
Choosing between them is a matter of taste, but knowing the visual effects of each helps you find the one that speaks to your style.
Why We Care About Cut
Cut is often the quietest of the 4 Cs, less immediately visible than carat or color, but it has the biggest impact on a diamond’s beauty. It’s also where expertise makes all the difference.
At Greenwich St., we’ve spent decades studying diamonds not just by the numbers, but by how they look in real life. We’ve learned that brilliance isn’t always about perfection on paper, it’s about how a stone performs in motion, how it interacts with light, how it makes you feel when you see it.
Our selection process is grounded in that knowledge. We don’t rely solely on grading reports. We examine each diamond for light return, proportion, and presence, choosing the ones that deliver a kind of radiance you notice across a room.
This attention to cut isn’t just technical, it’s personal. It’s about offering diamonds that speak, that glow, that stay luminous through years of wear.
FAQs About Diamond Cut
What’s the best cut for brilliance?
The round brilliant cut is designed for maximum sparkle. Its 58 facets are precisely angled to reflect the most light, making it the most brilliant shape overall.
Does cut affect a diamond’s price?
Yes. A well-cut diamond can command a premium because it looks brighter and more lively, even if it has a smaller carat weight. In contrast, a poorly cut diamond may appear dull, even if it scores well in other areas.
Can I tell if a diamond is well-cut just by looking at it?
To some extent, yes. A well-cut diamond will appear bright, symmetrical, and lively. But subtleties in proportion and symmetry can be hard to detect without tools or training, which is why working with a jeweler you trust matters.
Which diamond cut looks the biggest?
Some shapes create the illusion of size better than others. Oval, pear, and marquise cuts often look larger than round diamonds of the same carat weight due to their elongated forms and spread.
Is cut more important than color or clarity?
For overall beauty and sparkle, yes. A well-cut diamond can make lower color or clarity grades less noticeable, while a poorly cut diamond can’t be saved by high grades alone.
Citations:
[1] Diamond Cut - https://4cs.gia.edu/en-us/diamond-cut/
[2] Diamond Cut: it’s more than shape - https://4cs.gia.edu/en-us/blog/diamond-cut-more-than-shape/
[3] The GIA Diamond Cut Grading System - https://www.gemsociety.org/article/gias-new-diamond-cut-grading-system/
