Shape is not cut
Shape is the outline of a diamond seen from above: round, oval, pear. Cut is how well its facets are made. A diamond of any shape can be well or badly cut.
Shapes fall into two families. Brilliant cuts have many small triangular and kite-shaped facets and are made for sparkle. Step cuts have long parallel facets, like a staircase, and are made for clear, slow flashes of light.
The ten shapes
The ratio under each shape is its length divided by its width, in the range most people find well proportioned.
Round brilliant
The most popular shape and the brightest. Its 57 or 58 facets are arranged to return as much light as possible. It suits every setting and never dates.
Ratio 1.00
Oval
A stretched round brilliant with nearly the same sparkle. It looks larger than a round of the same weight and lengthens the finger.
Ratio 1.35 to 1.50
Cushion
A square or rectangle with rounded corners and large facets. Softer and more romantic than a round, with broad flashes of light.
Ratio 1.00 to 1.20
Emerald
A rectangle with cut corners and long, parallel step facets. It gives calm flashes instead of sparkle and shows the clarity of the stone.
Ratio 1.30 to 1.50
Pear
Round at one end and pointed at the other. Worn with the point towards the nail, it lengthens the hand. The point should be protected by a claw.
Ratio 1.45 to 1.75
Marquise
A long shape with two points. It has the largest face of any shape for its weight, so it looks bigger than it weighs.
Ratio 1.75 to 2.15
Princess
A square brilliant with sharp corners. Almost as bright as a round. The corners need the protection of a claw or a bezel.
Ratio 1.00 to 1.05
Radiant
The outline of an emerald cut with the facets of a brilliant. Bright, lively and strong at the corners.
Ratio 1.00 to 1.35
Asscher
A square step cut with deeply cut corners. Looking into it is like looking down a hall of mirrors.
Ratio 1.00 to 1.05
Heart
A brilliant cut in the shape of a heart. It needs a good cutter, since the two halves must match, and it reads best above one carat.
Ratio 0.90 to 1.10
Which shapes look largest
For the same carat weight, long shapes cover more of the finger. Marquise, pear and oval diamonds look the largest. Asscher, cushion and princess cuts carry more of their weight in depth and look the smallest.
Long shapes can show a bow tie, a dark band across the middle of the stone. A faint one is normal. A strong one is a sign of a poor cut, and it is worth seeing the stone before choosing it.
How to choose
- For the most sparkle, choose a round brilliant, then an oval or a radiant.
- For size on the hand, choose an oval, a pear or a marquise.
- For a quiet, architectural look, choose an emerald or an Asscher cut.
- For a softer outline, choose a cushion.
Every shape here is available as a lab-grown diamond. See them set in the engagement rings, or read about grades in the four Cs.
