CHAPTER 12 | CHOOSING THE SHAPE OF YOUR STONE

Diamonds and gemstones come in a surprisingly wide range of shapes, sizes and proportions, and some work better than others, especially in a ring. There is a lot to be said for choosing one of the less common shapes for your ring as it will enhance the more personal nature of the design.

Better quality and larger size precious stones will be cut to maximise their beauty and carat weight rather than to fit to standard sizes. So your ring should be made around your gem, rather than the gem supplied to fit a standard ring mount.

Read on - or Download Chapter 12 as a pdf to read at your leisure.

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SUMMARY

• There is a wide range of shapes available for both diamonds and gemstones

• Shape and cut are intimately linked, and the quality of cut influences the desirability and price of a stone

• Shapes with pointed corners can be damaged in claw settings, and you should avoid round stones with a ‘culet’ at the point

• Simpler cuts often require higher grade and more expensive stones

• Older stone cuts and shapes can be difficult to match, and less popular shapes can be difficult to source.

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SHAPE AND CUT

There are twelve principle shapes for diamonds and fifteen principle shapes for gemstones. Shape and cut are separate elements but are linked – a shape can determine which cuts are possible, but there may be more than one cut suitable to a shape. For example, a square shaped stone may be ‘princess’ cut or stepped. The former is sparklier as there are more facets to the princess cut.

Among diamond and gemstone shapes there is obviously a great deal of overlap, but there are differences in the way gemstones and diamonds are cut, and a distinction is sometimes made between ‘faceted’, which is a standard gemstone cut, and ‘diamond cut’ as a term applied to gemstones. Diamond cut tends to be a brighter cut for the stone as it involves more facets and more cutting. Not all gemstones are suitable for this treatment as some are either too brittle or too soft to withstand the extra pressure and work it involves.

The less popular or less common shapes can be difficult to source when you want a particular stone, so it may be a case of ‘first catch your gemstone’. As long as you allow time in your design process nothing is impossible as stones can be specially cut to order from the rough.

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POINTS TO NOTE

There are some things you should consider when choosing the shape of your diamond or gemstone. Stones with pointed corners, like square cuts, marquise and pear shapes, can be fragile at the points. This is one reason why re-setting old jewellery can be problematic.

Three of these shapes are also the most difficult to set in claws in a visually pleasing way because of the problem of positioning the claws such that they hold the stone securely but do not materially change the whole look of the piece.

Bezel setting (Chapter 13) is a good alternative for these shapes as long as it is designed to maximise the amount of light entering the stone. Bezels also protect the edges of brittle and soft stones.

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DIAMOND SHAPES

If we start with diamonds, the most popular shape is obviously the round brilliant cut. There are also ‘modified brilliant cuts’ where brilliant cut faceting is applied to different shapes of stone. This group includes oval, marquise, heart, pear-shape, radiant cut (relatively new), trillion (triangle), and antique cushion cut (rectangular or square with rounded corners).

Other shapes include the emerald cut, a simpler cut originally devised for softer, more brittle emeralds, and the baguette cut, including the tapered trapezoid baguette. This latter is another very simple cut with few facets which is generally used for side stones. Both emerald and baguette cuts require higher quality diamonds; because they have fewer facets and are less ‘brilliant’ in appearance, any inclusions are much easier to see, so stones with few obvious facets tend to be selected for these cuts. This can make them more expensive per carat on average than other options.

The Asscher cut is another traditional cut for diamonds. Sophisticated and less common than many of the other rectangular shapes, it has a few more facets than the emerald cut, and is usually used for a more ‘square’ shape.

Finally, the princess cut is the square stone with pointy corners which has a lot of facets and high brilliance. It is a popular shape, but it is worth bearing in mind that, although diamond is the hardest mineral known to man, it can be brittle and is not indestructible.

I have seen princess cut diamonds which have been damaged in the corners when being claw-set. This damage is not immediately apparent until the time comes to reset the stones, or even just to repair the inevitable wear on a ring which is worn daily. Dismounting the stones to perform this work reveals the cracks or chips in the diamond corners, so you cannot always know whether any stone is in good enough condition to remount until it is removed from its setting.

Old fashioned diamond cuts. There are older diamond cuts including the ‘rose’ cut, Mazarin and ‘old European’. These have been superseded and are rarely produced now because they have a much lower level of brilliance than modern cuts.

They have their own charm and attractions, but are very difficult to match if you are trying to remount inherited jewellery. Older stones were almost always hand cut, and this inevitably limited what could be done with the stone.

GEMSTONE SHAPES

In gemstones, a round simply ‘faceted’ stone isn’t cut the same way as a diamond, and generally has fewer facets than the brilliant cut. This is also true of the oval, pear-shape, marquise, heart, antique cushion, triangle or trillion. Most of these cuts have fewer facets than diamonds of the same shape would have. Emerald and baguette cuts, as well as the

Asscher, are simpler and so usually the same as for diamonds, and the square cut is very similar to the princess cut.

There is also the ‘antique square cushion’ cut which has checker-board faceting on the top of the stone, and a ‘cushion’ cut, which is similar to the emerald cut. Unlike the emerald cut, which is actually octagonal, this doesn’t have its corners cut off.

PARTS OF A FACETED GEMSTONE

There are some basic terms that it might be useful for you to know when people talk about different parts of the gemstone. Take a look at this diagram of a typical brilliant cut stone.
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The flat top of the stone is called the table, the widest part is the girdle, and right at the bottom, you have what is known as the ‘culet’ (pronounced ‘kewlet’). This was originally introduced for round cuts to protect the bottom of the stone, and it does still appear in modern cut diamonds. Viewed from the top through the table, it may be visible in some clear stones, especially larger diamonds, as a dead or ‘black’ spot, not reflecting back as much light as the surrounding faceting. Generally speaking a culet is not desirable in a well cut diamond. If your diamond certificate indicates that a culet is present, you should view the stone before having it set in a ring.

The whole area above the girdle is called the ‘crown’. Below the girdle is the ‘pavilion’. There are different types of facet, depending on the cut, between the girdle and the flat top of the table on one hand, and between the girdle and the bottom of the stone on the other. The way in which these facets are cut will affect the brilliance of the stone.

The ratio of width to depth of any stone will impact on its brilliance because of the way the light comes into the stone and is reflected back out of it. This is discussed in more detail in .

CONCLUSION

The quality of cut of any gemstone is an important element in assessing its overall suitability, desirability and price. There is a surprisingly wide range of stone shapes available, and some are more suited to rings than others. The more uncommon the shape you choose, the more personal will be your ring, providing the shape of the stone does not compromise the integrity, beauty and practicality of the design.

The setting should be designed to protect vulnerable stone shapes as some with pointed corners can be damaged in claw settings, and you should try to avoid round stones with a ‘culet’.

The shape and cut are intimately linked and the simpler cuts often require higher grade and more expensive stones. There is a clear relationship between the depth of cut and the brilliance of a stone owing to the way light is reflected within the stone. This is particularly an issue with diamonds, less so with coloured stones, and is one of the determinants of diamond quality and price.

Older stone cuts and shapes can be more difficult to match when remodelling old jewellery, and less popular shapes can be difficult to source in any given coloured gemstone specification. So getting the colour, quality and shape combination you want in a pink sapphire, for example, may take a little while.

As long as you allow time to source your stone or perhaps have it cut to order, anything is possible, and it is often worth waiting for just the right stone as this will make all the difference to your ring.

Read On – Chapter 13 takes this a step further and looks at the issues relating to the style and design of your ring and what to be aware of when choosing.

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