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What is Diamond Cut?

Posted on 21st February 2015

Diamond cut

In the final part of our 'What is?' series, we focus on 'diamond cut', some industry experts would say this is the most important part of purchasing a diamond. Using the Gemological Institute of America's (GIA) grading system, we will go into depth and give advice on what to look for and what questions to ask.

Diamond cut is considered to be the most challenging component of diamond grading to assess. More thought and consideration is required in order to determine a diamond's true cut grade. Although some refer to diamond cuts as the shape, for example, marquise or princess (see diamond shapes), diamond cut actually refers to how well a diamond has been transformed from its rough form to its polished state and how well this diamond gives off brilliance and refracts light, most people want a sparkly diamond after all!

How cut is graded

A diamond's cut is graded using three factors for a round brilliant cut, namely cut, polish and symmetry and two factors for a fancy shape (any diamond shape that isn't a round brilliant cut), namely polish and symmetry. We have a large amount of customers who walk into our store and say 'we want a good cut or above', but when we ask 'how about the polish and symmetry?' most customers look baffled, especially when we tell customers that there isn't a cut grade on a fancy shape.This is something that needs to be explained throughout the industry to give consumers the ability to make an informed choice about what diamond to purchase.

Each one of these factors is assigned a descriptive grading, usually peaking at 'excellent', however some grading laboratories will use the term 'ideal' (The IGI sometimes adds the comment 'ideal cut' into the 'comments' section on their round brilliant cut grading reports). The excellent grade indicates that a diamond has been produced to perfection in its particular field, whether it be cut, polish or symmetry.

The below chart shows how diamond cut grades are determined.


Below we'll explain what the cut, polish and symmetry are and how they affect the brilliance of your diamond.


Diamond cut takes into account various dimensional aspects of a given diamond, once the rough diamond has been cut into the finished shape. Diamond graders focus on the level of craftsmanship that has been used to create the diamond and the level of perfection the different aspects have been produced to.The factors that are scrutinsed, both individually and in relation to one another, are; table, crown, girdle, pavilion and culet.


Diamond polish refers to how well each facet has been polished after a particular diamond has been cut from its rough to polished form. Diamonds, once cut, are polished using a polishing wheel. This wheel can leave small defects across the surface of the diamond, which if severe enough can sometimes disrupt light flow through the diamond and reflection from the diamond's surface.


Symmetry refers to how symmetrical a diamond's facets are and their effect on the brilliance of the diamond. Symmetry also takes into consideration irregularly formed and located facets, tables, culets and girdles, which can affect the brilliance.


Diamond cut takes into consideration a lot of parameters in order to grade a diamonds brilliance, not the diamonds shape. There are three factors that are graded, these are the cut, polish & symmetry, these sections are graded using the terms, excellent (superior brilliance), very good, good, fair and poor (least favorable).

Our advice

Remember that diamond grading is opinion based, we recommend that you visit your local jewellers and observe the various types of diamond cuts ranging from excellent to good. Remember that different shape diamonds will reflect light differently, seeing which shape offers the most pleasing sparkle to your eye is the most important factor.

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