Diamond Shapes: The Complete Guide
Shape is the first decision almost everyone makes about a diamond, and it is the one decision no grading report can make for you. A report will tell you a stone's colour, its clarity and its carat weight. It will not tell you whether an oval flatters your hand, why one cushion glitters like crushed ice while another flashes in broad panels, or why an emerald cut demands a cleaner stone than a round at the same price. Written by a GIA Graduate Gemologist who cuts, sets and repairs these stones daily in London, Ontario, this guide covers every diamond shape you are likely to encounter: the ten classics, the step cuts and antique cuts, and the shapes lab-grown diamonds have brought back into the mainstream.
Shape Is Not the Same as Cut
The two words get used interchangeably in shop windows, and they mean different things. Shape is the outline of the stone viewed from above: round, oval, emerald, pear. Cut is how well that stone was actually made: the proportions of its crown and pavilion, the angles of its facets, the precision of its polish and symmetry, and ultimately how much light it returns to your eye.
Two ovals of identical carat weight, colour and clarity can look nothing alike, and the difference is cut. This is the single most important thing to understand before you shop, because cut is where your money either works for you or quietly disappears.
The Three Faceting Styles
Every diamond on this page belongs to one of three families, and the family determines how the stone behaves in light.
Brilliant cuts use triangular and kite-shaped facets radiating from the centre. They are engineered for maximum light return, and they produce the fast, bright sparkle most people picture when they think of a diamond. Rounds, ovals, pears, marquise, cushions, princess and hearts are all brilliants.
Step cuts use long, parallel, rectangular facets arranged in tiers, like the steps of a staircase. Instead of sparkle they give broad flashes of light and shadow, the hall-of-mirrors effect. Emerald, Asscher and baguette cuts are step cuts. Because there is nowhere for an inclusion to hide, step cuts are held to a higher clarity standard.
Mixed cuts combine both. The radiant is the best-known example: an emerald cut's outline over brilliant faceting.
The rose cut sits outside all three. It has a flat back and no pavilion at all, and it gives lustre rather than fire.
What GIA Actually Grades, and What It Doesn't
This is where most shape guides are out of date, and it matters to what you buy.
GIA issues an overall cut grade for round brilliant diamonds only. Every fancy shape, from oval to cushion to emerald to pear, receives grades for polish and symmetry but no overall cut grade. That means the familiar triple-excellent only exists for rounds. For every other shape, cut quality is assessed by a trained eye, not read off a report. GIA has announced that it will introduce cut grades for marquise, oval and pear-shaped diamonds beginning in 2027.
Lab-grown reports changed on 1 October 2025. GIA no longer issues 4Cs colour and clarity grades for laboratory-grown diamonds. It assigns a descriptive assessment instead, Premium or Standard, because the great majority of lab-grown material falls into a narrow band of colour and clarity. Reports from IGI and other laboratories still use the traditional 4Cs scale, which is why a lab-grown diamond's paperwork can look very different depending on who graded it.
The practical takeaway is the same either way: with any shape other than a round, the report is a starting point and your eye is the judge. Come and look at the stone.
The Classic Diamond Shapes
Ten shapes account for almost every diamond sold. Each one below lists the faceting style it belongs to, the terminology a GIA report actually uses, the length-to-width ratio most buyers prefer, and the one thing to watch for before you commit.
Round Brilliant
GIA report term: Round Brilliant
Fifty-seven or fifty-eight facets arranged to return the maximum amount of light back to the eye. It is the most studied outline in gemmology and the benchmark every other shape is measured against for brightness, fire and scintillation. It is also the only shape that currently receives a GIA cut grade, which makes it the easiest diamond to buy with confidence from paper alone.
Oval
GIA report term: Oval Brilliant / Oval Modified Brilliant
A round brilliant stretched along one axis. The elongation flatters the finger and makes a stone read larger face-up than a round of the same weight, which is why it has been the most requested engagement shape for several years running.
Cushion
GIA report term: Cushion Brilliant / Cushion Modified Brilliant
A square-to-rectangular outline with rounded corners, descended from the old mine cuts of the 19th century. Modern cushions come in two personalities: chunky, with large open facets and clear flashes of light, or crushed ice, with many small facets that shatter light into a glittering, softer sparkle.
Princess
GIA report term: Square Modified Brilliant
A square brilliant with sharp, uncovered corners and a crisp, contemporary line. It retains more of the original rough than almost any other shape, so it typically costs less per carat than a round of comparable quality.
Emerald
GIA report term: Emerald Cut
A rectangular step cut with cut corners and long parallel facets that produce the hall-of-mirrors effect: broad flashes of light and shadow rather than sparkle. It is the most architectural of the shapes and the most flattering to a long finger.
Asscher
GIA report term: Square Emerald Cut
A square step cut with pronounced cut corners and concentric facets that draw the eye down to the centre, the windmill effect. Developed in Amsterdam in 1902 and revived heavily in the Art Deco period.
Radiant
GIA report term: Cut-Cornered Rectangular (or Square) Modified Brilliant
The hybrid: the outline and cut corners of an emerald cut with brilliant faceting underneath. You get the clean geometry of a step cut with the fire of a round, and the cut corners make it far more durable than a princess.
Pear
GIA report term: Pear Brilliant / Pear Modified Brilliant
A round at one end tapering to a single point at the other, a teardrop. Worn with the point toward the fingernail it lengthens the hand, and it carries its weight very efficiently face-up.
Marquise
GIA report term: Marquise Brilliant
An elongated boat shape, also called a navette, with a point at each end. Of all the shapes it delivers the largest apparent size per carat, and it is the most dramatic on the hand.
Heart
GIA report term: Heart Brilliant / Heart Modified Brilliant
Essentially a pear with a cleft cut into the rounded end. It is the most technically demanding outline to cut well, because the two lobes must be identical and the cleft must be sharp and distinct.
Step Cuts, Side Stones and Antique Cuts
These rarely headline a ring on their own, but they define its character: as accent stones, in three-stone designs, and in the period and estate pieces that come across my bench every week.
Baguette and Tapered Baguette
GIA report term: Straight Baguette / Tapered Baguette
Small rectangular step cuts, straight-sided or tapering to one end. The signature Art Deco accent, and still the cleanest way to flank a centre stone without competing with it.
Trilliant
GIA report term: Triangular Brilliant / Modified Triangular Brilliant
A triangular brilliant with either straight or gently curved sides. Bold as a centre stone, and the most common shape for the flanking stones in a classic three-stone engagement ring.
Half-Moon and Trapezoid
GIA report term: Half-Moon Brilliant / Trapezoid Step or Brilliant
Purpose-cut side stones. The half-moon nestles against a round or oval centre; the trapezoid sits flush beside an emerald, radiant or cushion. Both exist to make a three-stone ring look like one continuous object rather than three separate diamonds.
Old European Cut
GIA report term: Old European Brilliant
The round brilliant's direct ancestor, cut by hand from roughly the 1890s to the 1930s. A small table, a tall crown, a deep pavilion and often an open culet give it a warm, candlelit glow rather than modern brightness.
Old Mine Cut
GIA report term: Old Mine Brilliant
The cushion-shaped hand-cut predecessor to the Old European: squarish outline, high crown, open culet. Cut to follow the natural octahedral rough rather than to maximise brightness, which is exactly why collectors want them.
Rose Cut
GIA report term: Rose Cut
Flat on the back with a domed, triangular-faceted crown and no pavilion at all. It gives a soft, watery lustre instead of sparkle, spreads very wide for its weight, and sits low enough to wear under a glove.
Shapes Made Popular by Lab-Grown Diamonds
A point of honesty first, because you will read the opposite elsewhere: lab-grown diamonds have not created any shape that cannot be cut in a natural diamond. The material is the same, the cutting is the same, and every outline below has existed in gemmology for decades or centuries. What changed is economics and rough supply, and that has genuinely changed what walks through my door.
Hexagon
Six-sided, cut either as a step cut with crisp parallel rows or as a brilliant. It was a rare novelty in natural diamond and is now one of the most requested alternative outlines in lab-grown, especially in elongated form as a bezel-set solitaire.
Kite
A four-sided shape with two long sides and two short ones, set point-up or on an angle. Extremely efficient to cut from a flat plate of rough, which is precisely the form CVD-grown material arrives in.
Shield
A triangular outline with cut corners and a broad, flat top. Historically a side stone; now regularly ordered as a centre stone in the sizes lab-grown makes affordable.
Elongated Cushion and Radiant
Not new shapes, new proportions. Stretching a cushion or radiant past a 1.30 ratio wastes rough, and in natural diamond that waste is expensive. At lab-grown prices a cutter can chase the look instead of the yield, which is why long, narrow cushions and radiants are suddenly everywhere.
Old Mine Brilliant Revival
Modern stones cut deliberately in the antique style: high crown, small table, open culet, chunky facets. In natural diamond that means either hunting for a genuine antique or sacrificing serious weight to recut one. In lab-grown it is simply a cutting choice, so the antique look is now available new, clean, and in matched pairs.
Portuguese and Antwerp-Style Cuts
Heavily faceted specialty cuts: tiers of facets in the Portuguese, step-cut and brilliant elements combined in the Antwerp and Criss styles. They demand deep rough and enormous cutting time, which historically made them collector items. Lab-grown supply has moved them within reach of an ordinary custom budget.
Why Lab-Grown Changed Which Shapes Get Cut
Three things, and none of them involve new gemmology.
Cost per carat. Fancy outlines like hexagons, kites and long, narrow cushions waste a great deal of rough. In natural diamond that waste is priced into the stone, so cutters play it safe and cut what reliably sells. At lab-grown prices a cutter can afford to chase a look instead of a yield, and shapes that were commercially unviable become worth cutting.
The shape of the rough itself. Natural diamond crystallises as an octahedron, two pyramids base to base, which is why the round brilliant and the classic fancy shapes evolved as they did. CVD-grown material grows as flat tabular plates and HPHT material as cuboids. Different starting geometry favours different outlines, and flat, angular shapes like kites, shields and hexagons cut very efficiently from a plate.
Size at a reachable price. Shields, trilliants and half-moons were historically side stones because a large one was prohibitively expensive. At lab-grown prices they can headline a ring.
None of this makes a lab-grown diamond a different material. It is diamond, chemically and optically, and the cutting science is identical. What lab-grown changed is which of these shapes a normal budget can actually reach. If you are weighing the two, read my honest comparison of lab-grown and natural diamonds.
How to Choose Your Shape
Start with the hand, not the chart. Elongated shapes, meaning oval, marquise, pear, emerald, elongated cushion and radiant, lengthen the finger. Round, princess, Asscher and square cushions read compact and bold. There is no rule beyond what looks right on the person wearing it, which is why trying stones on matters more than any list.
Match the shape to the life. Princess and trilliant corners, and pear, marquise and heart points, are the parts that catch and chip. They are perfectly wearable, they simply need to be set properly with V-prongs or a bezel and checked once a year. If you work with your hands, a bezel-set oval or a well-protected round will give you the least trouble.
Let the shape set the clarity budget. Step cuts show everything, so with an emerald or Asscher you spend on clarity. Crushed-ice brilliants hide a great deal, so with a cushion or radiant you can drop a clarity grade or two and put the money into size or cut instead. If the grading terms are unfamiliar, start with my guide to the 4Cs of diamonds.
Spend on cut before carat. A well-cut 1.00 ct will outshine a poorly cut 1.25 ct every time, and it will keep doing it for fifty years.
Diamond Shape FAQs
Which diamond shape looks the biggest for its weight?
Marquise, then pear and oval. Elongated shapes spread their weight across a wider face-up area, so they look larger than a round of the same carat weight.
Which diamond shape is the most expensive?
The round brilliant, per carat. It requires the most rough to be cut away to reach its final form, and that waste is priced into the stone. Princess, cushion and radiant cuts retain more of the rough and generally cost less per carat.
What is a bow-tie in a diamond?
A dark band across the centre of an elongated brilliant such as an oval, pear or marquise, caused by light leaking out of the bottom of the stone instead of returning to your eye. Every elongated brilliant has one to some degree. A good cut makes it faint enough that you stop noticing it, and no grading report records it. You have to look.
Does GIA give a cut grade to fancy shape diamonds?
Not currently. GIA issues an overall cut grade for round brilliant diamonds only; fancy shapes receive polish and symmetry grades instead. GIA has announced cut grades for marquise, oval and pear shapes beginning in 2027.
Are there diamond shapes that only exist in lab-grown diamonds?
No. Lab-grown and natural diamonds are the same material and are cut by the same methods, so any shape that can be cut in one can be cut in the other. What lab-grown changed is price and rough supply, which made shapes like hexagons, kites, shields, elongated cushions and antique-style old mine cuts affordable enough to become common.
Which diamond shape is best for an engagement ring?
The one the wearer keeps looking at. Round and oval are the two most requested, but shape is the one part of a diamond that is purely personal, which is exactly why it is worth seeing stones in person rather than on a screen.
Can a diamond be recut into a different shape?
Sometimes. A stone can be recut to remove damage or to change its outline, but it always loses weight, and how much depends on the existing proportions and where the inclusions sit. It is worth a proper assessment before you decide, particularly with an inherited or antique stone.
See Diamond Shapes in Person, in London, Ontario
Photographs flatten a diamond. Bow-ties disappear, crushed ice looks like chunky faceting, and every stone on a screen looks bright. The only honest way to choose a shape is to hold a few of them under real light and see which one you keep coming back to.
I keep loose lab-grown and natural diamonds in a range of shapes, and I build the ring around your stone on site: designed, cast, set and finished at my own bench. Bring in an inherited stone and I will assess it, tell you what it actually is, and show you what it could become. If you want to see how that process runs, here is how I make a custom engagement ring, start to finish.
Daniel A Jewellery, 467 Wharncliffe Road South, Unit 3, London, ON N6J 2M9. Phone: (519) 660-8383.