• Choosing: A Diamond Shape

Choosing: A Diamond Shape

Choosing: A Diamond Shape

If you hear the word ‘diamond’ the chances are that the image in your mind will be a round stone resembling the classic round brilliant cut.  This is by far the most popular shape for diamonds, but there are many others available and if you would prefer something a little more unusual, the choice is yours.  In this blog we will take a closer look at some of the shapes available to you when choosing a diamond.

(To make it easier to understand this discussion you may find it helpful to read our blog on the anatomy of a diamond before continuing.  It defines the terms used to refer to different parts of a diamond and explains key aspects of these.) 

The round brilliant cut is classic.  It was developed specifically for diamonds and is the shape in which you will most often see them.  Diamond cutters worked for generations to perfect the proportions and faceting arrangement that would unlock the sparkling potential of the stone, altering the relative sizes and angles of facets to create the maximum return of light.  For a diamond to have the brightness and brilliance it is famous for it must achieve ‘total internal reflection’.  This happens when light entering the stone through the table reflects off the inside of the pavilion facets and is eventually returned to the viewer through the crown.  The modern round brilliant adheres to strict proportions so that it can achieve this, giving a great balance of brilliance and fire (respectively, the white and brightly coloured reflections from the stone).  If the stone varies by being too deep or too shallow, light may be lost through the back or sides instead of reflecting properly.  How well a round brilliant cut diamond meets these requirements is reflected in the ‘Cut’ grade on a lab report.


Shapes other than round brilliant are known as ‘fancy’ and include a whole range of modified brilliant cut styles as well as other varieties.  All other factors being equal the round brilliant cut will be brighter and more sparkly than other shapes, since in order to form the shape required the proportions of the stone will be compromised slightly.  What fancy shapes do offer is the opportunity to choose something a bit different and to find a shape that is attractive to you and flattering to your hand.  For these reasons, they are increasingly popular. 

Currently, the most popular fancy shape is the oval.  This elegant shape maintains the curves of the round but with an elongated outline that is very flattering.  It is a modified brilliant cut and wonderfully sparkly.  Of course, ovals can be long and narrow or short and squat and you will see both extremes and everything in between when choosing an oval diamond.  What you prefer will be personal choice, but generally we would select a balanced stone that is neither too long nor to short (as preferred by Goldilocks!).  However, it is very important that the symmetry is precise.  An oval that bulges more to one side or narrows more at one end will appear unbalanced – often you might know it looks wrong without quite being able to explain exactly why. 


Another popular shape is the pear.  This is really more of a teardrop shape and another modified brilliant cut with lovely sparkle.  It can also be seen in long and narrow or short and squat shapes and is ideally a balanced ‘in-between’ measurement.  A problem that can occur with fancy shapes including the oval and pear is extinction, often referred to as the ‘bow tie effect’, where the stone appears dark at its centre.  This is caused when the diamond does not reflect light properly and the viewer essentially sees the dark shadow of their head when they look at it.  Better cutting can prevent this, altering the angle at which the light is reflected and removing the problem.  Fancy shapes don’t have a ‘Cut’ grade, so experience is needed to look out for good proportions.  Where possible, they should always be viewed before purchase to be sure.

If a pear shape isn’t pointy enough for you then a marquise cut may be the answer.  This shape may be alternatively known as ‘navette’ and is reminiscent of a boat shape: basically, an oval with a point at each end and generally relatively long and narrow.  It has similar properties to ovals and pears and is a very elegant shape. 

If straight lines are more your thing, then the beautifully named princess cut offers a square modified brilliant shape with fantastic sparkle and fire.  Typically having a large table facet, the princess cut also demonstrates the unrivalled lustre of diamonds perfectly.  Care must be taken as the pointed corners are delicate, but the square shape is also the reason princess cuts can offer good value.  The typical octahedral form of rough diamonds is essentially two square-based pyramids base-to-base, so when cutting a princess cut with its square, pyramidal shape there is less waste than with many other cuts, giving a price advantage versus, for example, a round brilliant where making the round shape creates more waste.  Princess cuts are sleek and modern, giving something very different to the classic round brilliant.

A slightly confusing shape can be the octagon or emerald cut.  Typically rectangular with cut-off corners, the octagon is often known as the emerald cut because the shape was originally developed for emeralds, where it showcases the colour very well and the cut-off corners provide protection to the brittle stone.  It is a ‘step cut’ style with long rectangular facets.  Light reflecting from these gives bright flashes instead of intense sparkle, creating a completely different look to most other diamonds and enabling the brightness of the lustre and brilliance to be enjoyed to fabulous effect.  However, clarity becomes very important when choosing an emerald cut.  Since you can see right into the stone, inclusions that may not be noticeable in another shape may be much more obvious in an emerald cut.  In most shapes a VS2 clarity grading essentially guarantees the stone will be ‘eye-clean’ (with no inclusions visible to the unaided eye) while in an emerald cut this is not the case.  A very small inclusion under the table may be spotted with relative ease while still being small enough for the stone to be graded as a VS2.

The radiant cut offers the best of both worlds for those who want both a rectangular shape and sparkle.  Rectangular with cut-off corners like the emerald cut, the radiant is a modified brilliant with all the sparkle you would expect.  Proof that you can have your cake and eat it!

Antique jewellery can often contain diamonds that have a more ‘cushion-shaped’ appearance, a square or rectangular outline with curved corners that soften the shape.  If you like that look then a cushion shape could be for you.  Often a modified brilliant, this shape combines the flattering look of a square or rectangular outline with the brilliance of a round stone.  They work brilliantly in halo designs that accentuate their shape or as a solitaire with an antique-inspired feel.  Square cushion-shaped stones can look quite similar to rounds and are great if you want something different but not too different.

For the true romantics out there, the heart shape is also an option.  A modified brilliant with beautiful sparkle, the heart shape is essentially a squat pear shape with a nick taken out to give the classic heart outline.  Symmetry is of huge importance for this shape; if the two halves don’t match then this statement of love can look very unattractive. 

Because there is so much variety, fancy shapes are not given a grade for their proportions or ‘Cut’ on a lab report, but they are graded for their Polish and Symmetry.  The Polish grade refers to the evenness and brightness of the polish that the cutter has achieved and will be negatively affected if there are visible polishing lines making the surface appear uneven.  The Symmetry grade considers factors such as how accurate the sizes and shapes of the facets are, how neatly they meet, whether the crown and pavilion are aligned and if the overall outline is even and balanced.  With fancy shapes the symmetry is extremely important as it can particularly impact upon the overall shape of the stone.  Human eyes are very sensitive to symmetry and your eye will pick up on a problem even if you cannot quite express what it is. 

If you want to know more about the range of shape options available or need help choosing the one that is best suited to you, then speak to one of our gemmologists and diamond graders. 

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    PA Jewellery

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