Diamond Cut Guide

The cut of a diamond is the single factor that decides how a stone performs on the finger, and it is the one most often misunderstood. Cut is not the same thing as shape.

Cut refers to the precision of the proportions, the angles between the diamond’s facets, and the polish that controls how light enters, bounces around inside the stone, and returns to the eye. Get the cut right and even a modest diamond sparkles beautifully. Get it wrong and a perfectly white, internally clean stone can read flat and lifeless.

This diamond cut guide walks through what cut actually means, how diamonds are cut from rough to polished, the cut grades you should look for, and the most popular diamond shapes we set in our Mt Hawthorn workshop. By the end you will have a working framework for choosing the right cut for the engagement ring you have in mind.

What Diamond Cut Actually Means

Diamond cut refers to the geometry of the finished stone. It is a measure of how well the rough diamond has been transformed by a diamond cutter into a faceted gem that returns light. Diamond shape refers to the outline (round, oval, pear, princess and so on), while cut quality refers to how precisely that shape has been executed.

A well cut diamond uses every facet to redirect light back through the table, producing brilliant sparkle and brilliance that reads vividly even in low light. A poor cut allows light to leak out of the bottom of the stone, which is why a poorly cut diamond appears dull regardless of its colour or clarity grade. The cut grade is the only one of the 4 Cs that is entirely a function of human craftsmanship. Carat weight, colour and clarity are inherent to the rough; cut is created at the wheel.

The Cutting Process From Rough To Polished

Every cut diamond begins as a rough crystal pulled from a mine or grown in a laboratory. The diamond cutter studies the rough first, mapping internal inclusions, plotting the shape that will yield the most weight while preserving optical performance, and deciding where to cleave or saw the stone. Modern cutters use 3D scanning and laser tools to plan the cut before any material is removed.

Once the rough is shaped, the cutting process moves to faceting. Each facet is positioned at a specific angle to refract light correctly. The polishing process refines each surface to a mirror finish so light passes through the diamond cleanly rather than scattering at the surface. A round brilliant cut diamond carries 57 or 58 facets, each placed within tight tolerances. A poorly polished facet, even on a well shaped stone, kills the light return that gives a diamond its incredible sparkle.

Diamond Cut Grades Explained

The Gemological Institute of America grades cut on a five-tier scale: Excellent, Very Good, Good, Fair, and Poor. The grade reflects proportions, polish and symmetry combined. An Excellent cut diamond returns the maximum light possible for its shape. A Fair cut diamond loses noticeable light through the pavilion. A Poor cut diamond reads dull even in good light.

For round brilliant cut diamonds, we recommend Excellent cut as the standard, with Very Good acceptable when budget pressure makes it sensible. For fancy shapes, GIA does not assign a single cut grade in the same way, so the polish and symmetry grades become the proxy. We assess fancy cuts in person at the bench, looking for even faceting, well-aligned culets, and table widths that suit the shape. Two oval diamonds at the same carat weight and colour can read very differently depending on how the cutter handled the bow-tie effect through the centre of the stone.

The Round Brilliant Cut

The round brilliant is the most popular diamond cut and the most popular diamond shape we set, accounting for more than half of the engagement rings we deliver. Its 57 or 58 facets are mathematically optimised for maximum light return, which gives the round brilliant cut its reputation for intense sparkle. A perfectly proportioned round brilliant cut diamond reflects light from almost every angle, which is why it suits solitaire rings so well: the stone does not need surrounding accents to look alive on the finger.

The round brilliant works across most metals and most settings. It is the safest choice for buyers who want classic proportions and a diamond shape that reads consistently across decades of personal style.

Fancy Shapes And Brilliant Cuts

Fancy shapes covers everything that is not round, and most of them are still brilliant cuts at heart, with triangular and kite-shaped facets designed to refract light in a similar way to the round brilliant. The oval cut elongates the round shape and reads larger on the finger at the same carat weight, which makes oval diamonds a strong choice for buyers who want presence with slender fingers. The pear cut, sometimes called a teardrop, blends a rounded end with a point and suits a gallery setting that protects the tip.

The princess cut is a square silhouette with brilliant faceting through the pavilion, giving it brilliant sparkle in a more architectural shape. The cushion cut sits between a square and a round, with rounded corners that soften the outline and a faceting pattern that throws larger flashes of light. The marquise cut runs long and pointed, and reads very large on the finger because of its elongated shape, though it requires careful setting at both points.

Step Cut Diamonds

Step cut diamonds use long, rectangular facets arranged in parallel rows, like the steps of a staircase, rather than the triangular facets of brilliant cuts. The emerald cut is the best known step cut, with its rectangular shape, cropped corners and clean parallel lines. Step cut diamonds produce a different kind of light return: less of the rapid scintillation you see in a brilliant cut, more of a glassy, hall-of-mirrors flash through the table.

Because step cuts have fewer facets, they show inclusions more readily than brilliant cuts. We recommend higher clarity grades for emerald cut and asscher cut stones than we would for a round brilliant of the same size. The reward is a quieter, more architectural look that suits buyers drawn to clean lines and timeless elegance over maximum sparkle.

Mixed cut diamonds, like the radiant, combine step cut facets on the crown with brilliant cut facets on the pavilion to deliver a rectangular shape with more fire than a true emerald cut.

Choosing A Cut That Suits The Wearer

Diamond cut is not just a question of which shape sparkles most. It is also a question of personal style, hand shape and how the wearer lives. Slender fingers carry oval, marquise and pear cuts beautifully because the elongated shape lengthens the finger visually. Wider hands often suit cushion or round brilliant cuts where the stone sits compactly. Active wearers benefit from round, oval or cushion cuts where there are no sharp points to catch on clothing, while a princess cut needs a setting that protects its corners.

The face up appearance also varies between cuts. Oval and marquise cuts read larger than round or princess cuts at the same carat weight, while emerald and asscher cuts read slightly smaller because the step faceting reduces the apparent flash. We pull loose stones across multiple shapes for clients still deciding so the choice is made with a real diamond in hand rather than a screen image.

A Recent Busselton Commission

A couple from Busselton booked a virtual consultation with us last winter, drove up the next weekend, and spent two hours at our bench comparing five diamond shapes side by side. They had come in convinced they wanted a round brilliant. They left with a 1.6 carat oval set in 18 carat rose gold, on a hand-finished tapered band with a hidden milgrain accent under the bridge.

What changed the decision was holding both stones over a piece of black velvet under the bench lamp. The round brilliant threw beautiful sparkle, but the oval read significantly larger on the finger and elongated the wearer’s hand in a way the round did not. Build time was eight weeks. The proposal happened on the beach at Geographe Bay at sunset. They came back twelve weeks later to commission matching wedding bands shaped to nest around the oval setting.

Frequently Asked Questions

A few of the diamond cut questions we hear most often.

What Is The Best Diamond Cut For Sparkle?

The round brilliant cut returns the most light of any shape, which gives it the most intense sparkle. For buyers who want maximum brilliance, a well cut round is the safest answer. Cushion and oval cuts come close, with their own character of light flash.

Does Cut Affect Diamond Price?

Yes. Cut grade is one of the four factors that drive diamond price. Excellent cut stones command a premium over Very Good or Good cut stones of the same carat weight, colour and clarity. The premium is worth paying because cut is what makes the stone perform on the finger.

What Is The Most Popular Diamond Cut For Engagement Rings?

The round brilliant cut remains the most popular diamond cut for engagement rings worldwide and in our workshop. Oval and cushion cuts have grown significantly in popularity over the last decade and now sit second and third in the rings we deliver. Princess, emerald and pear follow.

Can I See The Cut Quality With The Naked Eye?

Yes. A poorly cut diamond reads visibly duller than a well cut one even at conversational distance. Cut affects how light enters the stone, how it bounces internally, and how much escapes back through the table, which is what the eye reads as sparkle.

How Do Diamond Experts Compare Cuts?

Trained diamond experts use a combination of magnification, light performance imaging, and direct visual comparison under controlled lighting. We do this in our showroom for any client weighing two stones at the same shape and grade, because the numbers on a certificate only tell part of the story.

Bring Your Cut Question To The Bench

Choosing a diamond cut is best done with stones in your hand under proper lighting. The differences between an Excellent and Very Good cut, or between a 1 carat oval and a 1 carat round, are real and visible, but they are also far easier to see in person than from a product photograph. We keep loose stones across all the most popular diamond shapes specifically so clients can do that comparison at our bench rather than guessing.

If you are at the diamond selection stage of your engagement ring, we invite you in for a cut comparison session. Bring an idea of the carat weight you are working toward, the metal you are leaning toward, and any photographs of diamond jewellery your partner already loves. We will lay out three or four candidate stones at the bench, walk through cut grades and light performance under the lamp, and help you settle on the cut that suits the wearer rather than the trend.

Arrange A Cut Comparison Session at our Mt Hawthorn studio, or browse the Diamond Rings we have set into recent commissions for inspiration.