The Cut of a Diamond

The cut of a diamond is one of the most critical factors in determining the overall brilliance, fire, and scintillation of a stone. It is also one of the four Cs that depends on human craftsmanship and machines, as opposed to the other three Cs determined by nature. Therefore, it is imperative to be familiar with all that goes into cutting an excellent-cut diamond to make an informed decision about your purchase and maximize your budget.

Summary

The cut is an important factor in assessing a diamond. The GIA offers a cut grade for round diamonds only, while the AGS offers it for round and other fancy-shaped diamonds. The former cut grade ranges from excellent to poor, and the latter from Ideal to Poor. Detailed information about assessing the cut of different shapes of diamonds is available on our website. For example, if you wanted to determine the cut grade of a round cut diamond, it would be best to refer to that page on our website.

When evaluating a diamond, one of the most important aspects that you should pay attention to is its cut quality. The other 3 Cs (color, clarity, and carat) are important too, but the cut determines the amount of sparkle that you will get from the diamond, which is essentially the point of buying a diamond in the first place. A properly cut diamond will have all its facets well-proportioned and angled to reflect and refract light properly, maximizing the good effects while preventing any light from escaping prematurely through the back of the stone. A well-cut stone will look brilliant and attractive, while one with substandard cutting will look dull and lifeless.

Very Important Tips to Know While Considering the Cut of a Diamond:

Some diamond cutters tend to save rough diamonds by cutting diamonds deeper. Therefore, it is critical to know that buying a deep-cut diamond is not necessarily in your best interest. For example, a 0.80 carat and a 1-carat diamond can be the same in appearance and size if the latter is cut deeper. Below, see some examples of deep-cut diamonds.

The second important point while selecting a slightly deeper cut diamond with the right proportions would be to look at its overall dimensions in millimeters. For example, you might come across a round-cut diamond with 64% depth. However, if it has a thinner girdle and a larger table size, it might make up for the lost size. Thus, one of the best ways to analyze the visual appearance of a stone is to look at its dimensions in millimeters, as shown below: 

We learn the following two important points from the table:

1. In round cut diamonds, slightly deeper cut diamonds will result in a smaller diamond depending on the stone (see the difference in mm or millimeters between excellent cut and very cut with depth at 64%).
2. In fancy cut diamonds, this may not always be true; you may get a slightly deeply cut diamond with the same or larger dimensions in mm as one with ideal proportions (Please note that fancy cut diamonds are cut differently, and the GIA has yet to agree on their ideal proportions). In this case, going for a slightly deeper fancy cut diamond with the right dimensions and a good table might not be a bad idea for the right price.

This brings us to the third important point about the cut of a diamond. It pertains to not overly emphasizing the importance of the cut, especially if you are on a budget. The cut is essential, but there is barely any difference between a very good cut and an excellent cut while looking at a diamond in person. The GIA is stringent, and a minor glitch can easily turn a diamond into a very good cut from an excellent range. Therefore, if the depth, table, and other proportions are right, do not hesitate to go for a very good cut diamond. The same advice applies while deciding on the polish and symmetry level of round and fancy-cut diamonds. An excellent cut is great, but if the price bump is too much, it is probably not worth it.

The fourth and last point to take away is that you need to look at the cut proportions and details of each stone based on its shape. Please remember that you cannot apply the instructions for selecting a round diamond to a radiant-cut diamond. Follow our guides below for each shape to know exactly what to look for and how to determine proportions:

Round Cut Diamond, Princess Cut Diamond, Oval Cut Diamond, Cushion Cut Diamond, Emerald Cut Diamond, Radiant Cut Diamond,  Marquise cut Diamond, and Asscher Cut Diamond.

How is Diamond Cut Determined?

Recently, we published an article explaining how brilliance is determined in a diamond. The article has two sections, each of which contradicts the other. The first section outlines  ideals proportions for round and non-round-cut diamonds. However, the second section discusses how the GIA has found that a diamond does not need to have certain rigid parameters or proportions to have excellent brilliance or that diamonds cut in different proportions can still obtain an equal level of brilliance.

To make the long story short, the cut of a diamond is a complicated matter, and for the average consumer, it is best to go with the industry's standards. For round-cut diamonds, follow the GIA's cutting grading first. Alternatively, you can utilize our summarized proportions in the article referenced above.

Background

The cut of a diamond is a very technical term. To an ordinary person with no exposure to the diamond market, it may sound something like the knifing of a diamond, but it is more than that. The cut is the characteristic of any diamond that encompasses its symmetry, proportions, and polish. Each of the above-listed factors has its predominant role in shaping a diamond, hence gathered under the umbrella of a simple term called cut.

The importance of cut when buying a diamond should not be doubted. It is the most crucial feature of any diamond that determines its market value. Every diamond has certain facets whose alignment determines its symmetry and cut. As the word reflects, Polish is the smoothness and shine of a diamond that demonstrates its sparkle and attraction. So, one can say that it is the supreme property of a diamond to reflect light, creating a beautiful sparkle that can be translated into three different effects: brightness, fire, and scintillation. Brightness here is the intrinsic ability of a diamond to reflect white light, while fire is the typical rainbow effect. Scintillation is a quantitative and a qualitative term since it refers to the amount of sparkle and reflects the diamond's ability to produce a striated pattern of light and dark areas caused by reflections.

The shape of a diamond in which a raw diamond is cut is sometimes confused with the cut. Diamonds are cut into steep, fancy, or mixed cuts based on the original form of the diamond. The popularity of certain shapes, internal features/flaws of the raw diamond, and preservation of carats of the diamond are a few other factors that can influence the cut of a diamond. Every diamond cutter wants to get the best final diamond product from the cut with the least amount of carat waste and the best brilliance with the least amount of light leakage out of a diamond.

For a customer, cutis the most challenging factor to judge out of the 4Cs of a diamond. It is graded according to different standards. The GIA offers the easiest; it has five grades, including Excellent, Very Good, Good, Fair, and Poor. The higher the grade of a cut, the greater the value of that diamond. Please note that the empirical and mathematical side of the process can result in a tremendous and sparkling diamond. Technology has started to play its role, and the reliance on technical labor for the cutting process is declining in many parts of the world.