When thinking about the shape of your diamond, don't confuse this term with a diamond's cut. While cut is all about facets, angles and symmetry, shape refers to the outline of the diamond when viewed face on - imagine looking down on it when it's on your finger, or mounted in a necklace or earring.
Each shape has its own unique characteristics so choose carefully to fit the design you have in mind. Both cut and shape are important because they enhance the diamond's brilliance (reflected white light) and fire (flashes of spectral colours) to differing effects.
This is the most popular and traditional cut. Designed along precise mathematical guidelines, this shape maximises both brilliance and fire. The modern round brilliant has 57 facets (polished faces) and special attention is paid to the proportions of the cut to ensure perfect symmetry and encourage the total internal reflection of light within the stone. Stones that are cut to the highest grade demonstrate the most spectacular effects of brilliance and dispersion (see diamond Cut).
Oval diamonds demonstrate a similar brilliance to the traditional round brilliant cut. Traditional oval diamonds have a ratio of 1.5:1.0 where the length of the stone is about one and a half times the width but relative proportions can vary considerably. If you decide on a design that places the stone along the finger, bear in mind that longer ovals - with a higher length-to-width ratio - are considered to be more flattering because they have a lengthening effect on the hand.
Another variation of the traditional round brilliant cut round diamond, the marquise (or navette) is oval in shape with elegantly pointed ends. Louis XIV, inspired by the smile of the Marquise de Pompadour, was the first to commission this design. It's a shape that works particularly well when used in combination with smaller stones and, like the oval, is flattering to the hand when worn length-ways along the finger because it has an elongating effect.
The asymmetry of the pear (it's actually shaped more like a teardrop) gives it a unique appeal. The pear is a modified brilliant cut with levels of fire and brilliance approaching that of the traditional, round stone. However a badly proportioned pear can easily lose brilliance so choose your stone well. Also consider the stone's length-to-width ratio. Pear diamonds work extremely well in pendants or earrings.
This quintessential romantic diamond style, a heart stone is similar in both cut and shape to the pear but shaped at the top to form the curves of the heart. Typically this shape contains 59 facets and sparkles beautifully. If you choose a heart diamond, symmetry is important, not only for aesthetic reasons, but also to ensure optimum fire and brilliance. Make sure that the shape is pleasing to the eye - not too long and thin, not too square and not too flat.
The emerald cut, so called because it is the shape most often used for emeralds, has a rectangular outline with cropped corners and a series of flat, rectangular facets stepping down from a large, open 'table' (primary central) facet. A 1.50:1.00 ratio is usually considered best, meaning that the length of the stone is about 1½ times the width of the diamond. Loved by purists, the octagonal design produces a unique, glassy appearance, and as a result has great brilliance, and more of a sleek and smooth quality. Due to the open nature of this cut, flaws may be more easily visible, so take note of the diamond's clarity.
Developed in the 1970's, the princess cut is a modern classic design and has become the most popular of the so-called 'fancy' diamond cuts - the term used to describe all non-round stone shapes. Known technically as a square modified brilliant cut, the princess is square in shape but with more facets than an ordinary square diamond, making it more brilliant and sparkly. This shape is also perfect for Eternity Rings because the stones can be set alongside each other in a continuous band without gaps. When viewed from above, princess diamonds may appear more rectangular so make sure you choose the right dimensions for your design.
The Asscher cut is identical to the emerald cut in its octagonal shape, but is square in outline instead of rectangular. In fact, it is often referred to as the square emerald cut. Developed in 1902 by the Asscher Brothers of Holland, this diamond shape has classic historical qualities about it that has resulted in a resurgence in popularity over recent years. As with the emerald, it is important to consider diamonds of higher quality because flaws may be easily visible. Ideally the setting should not hide the blocked corners.
By combining some of the best features of the other diamond shapes, the radiant cut diamond is certainly one of the most beautiful designs. It is square or rectangular in shape with cropped corners, similar to the Asscher or Emerald cut but with a higher number of facets giving it all the sparkle and brilliance of the round and princess stones. For a radiant diamond shape that is square, look for length-to-width ratios between 1 and 1.05. For more of a rectangular shape, try length-to-width ratios greater than 1.10.
Cushion (or pillow-cut) diamonds are similar in shape to the radiant cut, but with softly rounded corners. Popular for more than a century, this diamond's large facets maximise its brilliance and highlight the stone's clarity. This shape is extremely pretty and comparatively rare so it is likely to stand out as being a little different if you choose it for your design. Cushion diamonds cut to a ratio of 1:1 are squarer in shape, while those with a ratio greater than 1:1.15 are more rectangular.