Diamonds are rated by three main metrics – the cut, clarity and carats. The cut is the shape and look of the diamond. The clarity is a measure of how clear and shiny it is, and the carat is a measure of size and weight. The clarity is not really something that can be changed – it depends on how the diamond is formed – but a large, rough, uncut diamond can be cut down and polished by a skilled diamond cutter to make it into a beautiful stone.
It’s a good idea to buy the nicest cut that you can afford within your budget, because cut is perhaps the most important thing for determining how a diamond looks. A diamond that is cut well will shine and sparkle brightly and catch the eye well. A bad cut will make the stone look cheap.
What the cut does
The cut is what determines how the diamond sparkles – a good cut will be ‘brilliant’, it will reflect light internally, bouncing it from one facet to another, with each acting like a mirror that directs the light through the diamond’s crown. If the diamond is cut too shallow, then it will lose light out of the bottom, making it look dull. If it is cut too deeply, or to narrow, then the light will escape through the sides. Neither of those is ideal.
There are a few different grades of cut – the best cuts are “ideal” – these are the most brilliant cuts, and they are quite expensive, but worth paying for if you can afford it. The next best is ‘excellent’ – these exquisite diamonds reflect almost all light through the top, and they still look exceptionally good.
Cheaper, but still good, is the ‘very good’ cut – for whatever reason (problems with the shape of the stone, or mistakes made by the cutter), these diamonds don’t reflect all light through the top, but they still have a good degree of brilliance. Diamonds with a ‘good’ cut are bright, but the flaws are apparent. The lowest tiers – fair and poor – have been cut imperfectly, and lose a lot of light. It would be unusual for someone to opt to use those in jewelry.
The cut is just one part of what makes a diamond special – there are a few different shapes that are popular with diamonds as well. The most common shapes are round, princess, asscher, emerald, radiand, heart, cushion, marquise, oval and pear.
Most people will be familiar with the round diamond. A round, brilliant cut diamond is something that is incredibly popular, and that diamond cutters have invested around 100 years of research into finding the perfect, most brilliant way to cut such a diamond to ensure that it produces the maximum amount of shine and light reflection. This is the kind of diamond that you are most likely to want in jewelry. Usually, when this diamond is cut, it will have 33 facets in the top (crown) and 25 in the bottom (pavilion). The proportions between each facet, and the way they are aligned, is what will determine whether the cut is brilliant or not. The ideal is something that is hard to achieve.
Princess cut diamonds are popular for engagement rings – this is usually a square diamond, but it can be made rectangular as well. If you are thinking of getting this kind of diamond, note that colors are very noticeable where the facets meet – so you should pick a diamond of a good color grade, and a good cut grade as well.
The emerald cut is a popular choice with people who are looking for something a little different to the traditional. It is a cut that has a large open table on the crown – and this helps to create a few broad flashes of brilliance, rather than the ‘sparkle’ of the more traditional cuts. The downside to this cut is that any flaws and inclusions are more noticeable, so you really do need to pick a very high quality cut, and something with a good grade of color and clarity.
The more unusual marquis and oval cuts, and the other more ornate cuts, are better in terms of error tolerance, but they still look best when they are cut well, clear, and have a good color grade. As a general rule of thumb, prioritise cut and clarity, then look at color and finally carat – a smaller but very high quality stone will invariably be more satisfying and more impressive looking than a big but dull or imperfect stone, so it does not pay to cut corners with the quality of your diamond – especially not if you plan to use it to make some heirloom jewelry.