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  • Writer's pictureSimo R.

Diamond Buying 101 Part 1 - Cut

Updated: Aug 12, 2022

When looking to buy a diamond for any reason, be it for a present, special occasion or just to show someone your appreciation, you will be quickly immersed in the world of numbers and letters that indicate a diamond's value. To help decipher some of these things I'm going to explain how diamonds are valued in the industry and what you should be looking for.

Firstly, what you should be looking for is what you can afford. Diamonds are amazing creations of nature and will always be held in high regard but you should never go overboard just to get 1 grade higher or something because the salesperson is pushing it on you. From my experience in the jewellery industry basically any salesperson will either be on commission or some kind of bonus system that will provide them a benefit for trying to upsell you. Resist their pressure and buy exactly what you know you can afford. A good jeweller will always be able to work with essentially any budget to find or create a beautiful piece of jewellery for any occasion.

When looking for a piece of diamond jewellery you may have heard of the 4Cs which are Cut, Clarity, Carat and Colour. The 4Cs have been around for many years and have become the standard on how we grade and buy diamonds and depending on the region of the world or who you are buying the diamond from there are a variety of systems to use when grading by these criteria. Nowadays however, I believe there should be 5Cs though with the emergence of origin tracking and lab created diamonds. The last C should be Creation (AKA origin).



Cut is probably the most important of the original 4Cs as you could have a beautifully coloured and flawless diamond but if it's cut poorly it won't show any brilliance or shine because the light won't interact with the diamond correctly. Cut is referring to two things, the shape the diamond is cut in, such as round, princess, emerald, etc., and the quality of the cut including proportions, meaning the angles, size and number of facets (flat spots) on the diamond, symmetry and polish.

When you're buying a diamond, it's best to identify the shape first of the diamond that you're looking for to help narrow down what kind you're looking for. There are also a variety of specialty cuts for most shapes. For example, the round cut stone could have a round transitional cut, a mixed cut, rose cut, or a variety of others but the most common is the round brilliant cut which has 57-58 facets. Once you've decided the shape and style of cut that catches your eye we move to the proportions of the cut.

As with many of the 4Cs, there are many different ways to indicate how well cut a stone is based on the proportions. These proportions are specific to the style of cut you have selected and are meant to maximize the brilliance and shine of the stone in diamonds. Here in Canada the most common grading system you'll probably hear of is the GIA (Gemological Institute of America) as they are one of the larger and well known labs in North America. The GIA cut grades from lowest to highest are: Poor, Fair, Good, Very Good, Excellent. Some people may say there is an Ideal cut as well under the GIA but in general, ideal cut stones can't be determined if they are mounted in a piece of jewellery and will be graded as if they were excellent cut.

The image above is a simple demonstration of what you might expect from the different cuts of diamonds but keep in mind that the method these are graded include a comparison to standard proportions so it can swing both ways. In the poor cut image for example some of the proportions are larger than the expected ones and the fair cut image has some proportions that are smaller but they could have been reversed as well. It just depends on how far off the proportions are from the accepted values that make the difference in cut.

Beyond the proportions of diamond there are also two other main factors that attribute to the cut rating which are symmetry and polish which are both exactly as they sounds. If a diamond is symmetrical then you will have a much better reaction with the light in all directions and therefore it will be graded higher in cut. The polish refers to how well the stone was polished which can also affect how light interacts with the stone. A highly polished stone is more desirable than a poorly polished one.

Some of the other grading systems used around the world include the AGS (American Gem Society) and the standards from CIBJO (The International World Jewellery Confederation).

CIBJO uses a similar style to the GIA and grades by either Poor, Fair/Medium, Good, Very Good and Excellent and they are used interchangeably with those from the GIA. However, the AGS uses their own system which starts with 0 and goes to 10. A 0 graded stone is an ideal cut diamond based on the proportions and the cut grade lowers as the numbers get higher to where a 10 on the AGS scale has a large variance from normal proportions and is considered a poor cut.

As a general statement, you would want to get as high of a cut grade as you can within your budget. It is actually worth lowering some of the other characteristics of your diamond, like colour, if you are able to get a better cut in many cases as a well cut stone will allow more light to interact with the diamond correctly and give you that brilliance and fire you would expect from a diamond.


If you are interested in getting your diamond appraised or even just graded or verified then visit us at 1612 Lasalle Blvd in Sudbury, Ontario, right next to Red Lobster and across from the Part Source. You can also contact us by email at or by phone at (705) 222-1221.

To read more about the services available check out our available services here.

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