Diamond cut buying guide

What is diamond cut?

Diamond cut refers to the way a diamond has been shaped and polished from its rough form. Some people refer to the shape of the diamond as the cut, for example a pear cut diamond, but the cut actually refers to a round shaped diamond’s ability to transmit light (and sparkle!). Round shape diamonds are the only shape given an official cut grade by certification laboratories - cut to 57 facets, sometimes 58. The 58th being a tiny flat facet at the bottom of the pavilion that’s known as the culet. The cut of a diamond is the most important factor that affects its brilliance, fire, and overall appearance. The better a diamond is cut, the more it will sparkle and reflect light. Always opt for an excellent cut round diamond, (ideal in IGI certified stones)

Light enters through the top of the stone, and refracts to give the sparkle! A stone that is too deep or shallow will not sparkle as much, such as a very good or good cut. So sticking to an excellent cut diamond ensures it’s within the top range of proportions, meaning it will be super sparkly. The GIA Diamond Cut Grading System for standard round brilliants in the D-to-Z color range is based on the assessment of seven components. The first three — brightness (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the pattern of light and dark areas and the flashes of light, or sparkle, when a diamond is moved) — are appearance-based aspects. The remaining four — weight ratio, durability, polish, and symmetry — are related to a diamond's design and craftsmanship. (Gemological Institute of America)

What diamond cut should I buy?

Always buy an excellent cut round diamond - its the most important factor for sparkle and beauty. You can dive deeper into diamond proportions to find a further optimum range within the excellent cut range, but I wouldn’t generally advise it, save your time - even an experienced expert wouldn’t be able to tell the difference to the naked eye between two excellent cut diamonds. If the GIA for example, with all their expertise and equipment, grade a diamond as an excellent cut, that’s good enough for me!

Fancy shape diamond "cut"

For all other shapes apart from round, known as fancy shape diamonds, they are not given a set cut grade by the grading laboratories, and come in different shapes - there is no such thing as an excellent cut oval, pear or any other shape. For this, the best thing to pay attention to is the measurements and proportions of the stone. Carat (ct) is just the weight, not necessarily the size. For example you can buy a 2ct oval diamond that is bigger or smaller than an average 2ct diamond - best to check the measurements of the stone. Confirm with your jeweller that the proportions of the stone are nice, not too deep or too shallow, and that it has a nice lustre (sparkle). Finding a slightly shallower stone to increase the visual size can mean a big saving - for example finding a 1.8ct stone that looks as big as your average 2ct could save you thousands of dollars (depending on the other grading factors too). Last thing to note is find a length/width ratio that you like for your choice of fancy diamond, as this directly correlates to the shape of the stone. For example you can get fatter looking oval with a ratio of 1.3 or a more elongated shape with a ratio of 1.6. Simply divide the length measurement by the width measurement to check the ratio of any stone.