Diamond Shapes, Cuts & Polishing

A diamond announces itself first by its outline. Before colour or clarity register, before the fire even catches the light, the eye reads the silhouette — round, square, teardrop — and forms a first impression of the whole stone. That outline is the shape; how the facets are arranged within it is the cut. The two are so often spoken of as one that in daily trade they blur, but the distinction is worth holding onto: shape is the mood you choose, cut is the craft that makes it shine.

This guide follows both, in three movements — the ten classic outlines and the single C each one asks you to watch, the wider and stranger family of fancy cuts that surrounds them, and the workshop journey by which a frosted crystal becomes a finished stone. It is, in miniature, the whole of what Antwerp has done to diamonds for five centuries.

• Round

  Classic

• Princess

  Trendy

• Emerald

  Glamour

• Asscher

  Vintage

• Cushion

  Romantic

• Marquise

  Dramatic

• Oval

  Innovative

• Pear

  Unique

• Radiant

  Diva

• Heart

  Sentimental

The ten shapes, and the C to watch

Every outline carries a character — a quiet shorthand for the mood it holds — and, more practically, each one steers your attention toward a different member of the Four Cs. Read that way, the ten classic shapes fall into three natural groups, and knowing which group you are in tells you where your budget will do the most good.

When the C to watch is Cut. The round brilliant is the most familiar outline of all, and the one against which every other is measured. Its modern geometry dates to 1919, when Marcel Tolkowsky calculated the proportions of a fifty-seven-facet round to draw the greatest possible brilliance and fire from a stone; roughly three diamonds in four sold today are cut this way. A round conceals nothing, so its single governing C is cut. The same holds for the modified brilliants that borrow its faceting and draw it into other silhouettes: the graceful oval, the long, pointed marquise — legend has it Louis XV commissioned the shape to mirror the smile of the Marquise de Pompadour — and the pear, or pendeloque, a teardrop whose ancestry reaches back to 1475 and the Scaif, the first wheel ever used to grind and polish a diamond. All three live or die by their proportions: a careless cut throws a faint bow-tie shadow across the centre. The heart, most sentimental of the shapes, follows no fixed formula at all, so proportion is everything — cut too plump or too thin, it loses its grace at once.

When the C to watch is Clarity. A second family trades scattered fire for broad, mirror-like flashes, and pays for it with candour: their wide, open facets leave nowhere for an inclusion to hide. The emerald cut — a step cut of long, measured lines first devised for emeralds — reads like a set of windows that let the eye travel deep into the stone. The asscher, the work of the Asscher Brothers of Holland in 1902, is essentially a square emerald, its stepped facets falling away in concentric squares. The soft-cornered cushion, sitting somewhere between the antique Old Mine cut and the oval, shares that open character and the same demand. In all three, clarity earns close attention — and, with so little sparkle to distract the eye, colour tends to show more plainly too.

When the C to watch is Carat. A last pair rewards the buyer who is watching value. The princess, a square face that marries a brilliant’s sparkle to clean geometry, emerged in the 1960s with one quiet economic virtue: where a round brilliant surrenders close to half its rough crystal to reach its proportions, a princess sheds only about a fifth — so a given budget buys a visibly larger stone. Guard its four points, though; they are vulnerable, and the setting should shield each corner. The radiant, Henry Grossbard’s 1977 marriage of the emerald step cut and the round brilliant, throws real fire from its seventy trimmed-corner facets, and because it is seen less often than a round it can offer honest value for the carat.

One footnote the trade knows well: shape is never purely cosmetic. The same open facets that expose an inclusion also spread colour evenly, which is why step cuts flatter an icy white — while the radiant and cushion, whose brilliant faceting gathers and concentrates hue, are the shapes a cutter reaches for when the aim is to deepen a fancy yellow or coax the most from a fancy-colour crystal. Choose the outline for its beauty, but know it is quietly working on the colour too.

Beyond the ten: the fancy-cut family

The ten classic shapes are a clearing in a much older forest. Around them stands the fancy-cut family — the forms the brilliant grew out of, the flat-backed roses of the candlelit centuries, the disciplined little cuts that frame a centre stone, and a handful of shapes invented purely for their own sake.

The round brilliant did not arrive whole; it was reasoned toward, cut by cut, across centuries. The line runs from the early Table and Mazarin cuts — little more than a polished window onto the crystal — through the high-crowned, small-tabled Old Mine and Old European cuts, the brilliant’s immediate forebears, made by candlelight and still beloved in antique jewellery. Once the modern brilliant was settled, cutters kept elaborating it — the Jubilee, the King, the many-faceted Royal 144 — variations on a theme already near perfection.

Older than the brilliant, and entirely its own idea, is the rose cut: a flat base and a dome of triangular facets rising to a point, like an opening bud. It gives a soft, romantic glow rather than sharp fire — the look of diamonds before electric light — and its family runs from the Dutch Rose to the Antwerp Rose that still carries this city’s name. Long out of fashion, the rose has lately returned for exactly the quiet, antique character that once retired it.

Not every diamond is meant to be the centre. A whole discipline exists for the small stones that line a shoulder or pavé a band: the simplified Single and Swiss cuts for the tiniest sizes, and above all the baguette and tapered baguette — clean rectangular step cuts that sit shoulder to shoulder — with the trapeze, lozenge and triangular trilliant shaped to flank a larger stone exactly. Newer still are the flower cuts — the Sunflower, Zinnia and Dahlia — whose facets bloom into petalled patterns: proof that a diamond can still be cut into very nearly whatever the mind imagines.

From rough to polished: the craft

For all this variety, every finished diamond passes through the same workshop — and most rough never reaches it. Of the millions of carats lifted from the earth each year, only about twenty per cent are gem quality and worth polishing. What turns a frosted, irregular crystal into a finished stone is a craft of three stages, the trade Antwerp has practised longer, and closer to perfectly, than anywhere on earth.

It begins, long before the first facet, with a single decision: which cut the rough will become. That choice made, the crystal is divided into its first rough shape — either cleaved by hand along the diamond’s natural grain, or sawn with a diamond-coated wheel or, today, a laser. It is the most consequential cut of all, because everything that follows is bounded by it.

Next the stone is given its outline. Two diamonds are set spinning against each other in opposite directions and gradually round one another down toward their girdle silhouette — bruting, the step where the old truth that a diamond can only be worked by another diamond is most visibly at play.

The final stage is itself three movements, and it is here the stone truly comes alive. In blocking, the first seventeen or eighteen facets are placed to establish the main geometry. In brillianteering, the remaining facets are cut — the step that sets the fire and brilliance. And in the final polishing, every facet is brought to a flawless, mirror-bright finish.

Choosing your outline

Put the three movements together and a simple way to choose emerges. Begin with the shape that suits the hand and the mood — that part is yours, and it is the one thing no grader can decide for you. Then let its governing C tell you where the money should go: a brilliant wants it spent on cut, an emerald or asscher on clarity, a princess or radiant on the extra size their kinder yield allows. One caveat rewards the careful buyer here: only the round brilliant carries a formal cut grade, from Excellent down to Poor. The fancy shapes are judged far more by eye — by proportion and symmetry than by any single line on a report — which is precisely why the merchant you trust counts for as much as the certificate. And remember that the outline you love is only ever as good as the workshop that made it — which is where a house that has watched the whole journey, from rough crystal to finished stone, earns its place beside you. When you are ready to choose your diamond, we are glad to guide the choosing.