Diamond shapes for engagement rings: shape vs cut

Shape is the outline you see from above. Cut is about how the stone is faceted and how well it handles light. The two words get mixed up, so "diamond cut" in a listing can mean either one. This guide explains the difference, then covers seven shapes for engagement rings using GIA's shape guide.

How is shape different from cut?

GIA says: "Shape describes the outline or silhouette of the diamond when viewed from above." It says cut style describes how the facets, the flat polished faces of the stone, are arranged and angled. The FTC says cut refers to how the diamond has been shaped, "taking into account the diamond's proportions, polish, and symmetry."

A cut grade is narrower still. GIA gives an official cut grade to round brilliants alone, on a scale from Excellent to Poor. Ovals, pears, and other fancy shapes have no GIA cut grade, so you judge them by their outline, symmetry, and look.

Brilliant or step cut: what changes?

GIA names two main cut styles. Brilliant cuts have many small facets, which GIA says can help hide inclusions and color. Step cuts have long, parallel facets that GIA says create a "hall of mirrors" effect and show color and clarity more. If you choose a step cut, GIA suggests going up in color and clarity grades.

Round

GIA says the round brilliant accounts for the majority of diamonds sold today and praises its sparkle. It is the shape with an official cut grade. GIA's buying tips also say: "Round brilliant diamonds tend to cost the most of all the shapes and cut styles."

Oval

An oval is a stretched round with brilliant faceting. GIA says its elongated outline can make fingers look longer and can make the stone look larger for its weight. GIA says to watch for the bowtie effect, "a dark, bow-tie shaped shadow that appears across the center of the stone." In a well cut oval it is faint.

What should you know about a pear shaped diamond?

A pear is a teardrop, rounded at one end and pointed at the other. GIA says the point of a pear shaped diamond is its weak spot, and it can be protected with a V-prong or a full bezel. GIA also says pears, like many fancy shapes, can show more color than a round brilliant does.

By tradition, GIA says, a pear shaped engagement ring is worn with the point facing away from the wearer. It says some brides wear the point toward them, and some choose a sideways setting. GIA advises checking the outline for even shoulders and wings, and looking for a subtle bowtie.

Emerald

An emerald cut is a rectangle with cropped corners and step-cut facets. GIA says the name refers to the cutting style, not the gemstone, and that its large table and open facets reveal inclusions and color more readily than other shapes do. GIA recommends higher clarity and color grades for emerald cuts, and higher still in larger stones.

Cushion

A cushion has a square or rectangular outline with rounded corners. GIA describes a softer, warmer sparkle and says cushions come with different facet patterns, some brighter than others. It says cushions can cost less per carat than round brilliants.

Princess

GIA calls the princess cut a square modified brilliant. It says the sharp corners need protection, ideally V-shaped prongs, or a bezel for full cover. GIA's ring care article says princess corners chip more readily because they lie close to a cleavage plane, a direction along which a diamond tends to split.

Marquise

A marquise is long and pointed at both ends. GIA says its outline gives the look of a bigger stone and can make the finger look longer. It says the tips are prone to chipping, so V-prongs or similar guards matter, and that symmetry is especially important because uneven sides show.

Sources: GIA 4Cs blog, Guide to Diamond Shapes for Engagement Rings; GIA 4Cs blog, Pear Shaped Diamond: Tips for Picking the Perfect One; GIA 4Cs blog, 10 Tips for Buying a Diamond Engagement Ring; GIA 4Cs blog, How to Protect Your Diamond Engagement Ring; FTC Consumer Advice, Buying Gemstones, Diamonds, and Pearls.