Your Guide to Diamond Quality: Cut

There are many things that go into selecting the perfect diamond. For someone like me, who has been around jewelry her whole life, finding the most beautiful stone can be so easy. But for those just dipping their toes in the jewelry water, or looking to make a one time purchase, the world of diamonds can seem a bit daunting. 

In this series of blog posts, I am revealing what it takes to find the perfect diamond, and how you can use this knowledge to get the perfect stone to meet all of your needs.  

A Brief Recap

In the mid-1920s, the Gemological Institute of America (the GIA) created a system for grading diamonds known as the 4Cs. These four criteria referred to the aspects of a diamond that they found to be most important when addressing quality: Carat Weight, Color, Clarity, and Cut. The first three have been discussed in previous blog posts, which can be read at the links above.

Carat weight is a measure of the mass of the diamond, measured in carats, with one carat equalling approximately 200g. Color, ironically, refers to a diamond’s lack of color, and is ranked on a scale from “D” to “Z”, with “D” being the highest color rating a diamond can receive. Clarity is a rating determined by the number and size of blemishes and inclusions found both within and without a diamond. All three of these things, in addition to cut, affect the quality of a diamond, and change the value of this precious gemstone. 

What Does Cut Refer To?

Cutting and shaping diamonds is an art form that requires a trained, precise hand. While we often think of a diamond’s shape (emerald, round, pear, etc.) as its cut, the GIA is actually grading a diamond based on how well it’s facets interact with light. This requires analyzing the proportions of a diamond, and evaluating how those proportions affect a diamond’s face-up appearance. 

Cut quality is one of the more technically difficult aspects of a diamond to evaluate. Not only does it require a little math, but it also calls for precise measurement, as well as familiarity with the design and craftsmanship of each diamond. The GIA cut grading system involves seven criteria: brightness, fire, scintillation, weight ratio, durability, polish, and symmetry. The first three are appearance-based aspects, evaluating how well the light is reflected within the diamond and the patterns they create. The second four are related to craftsmanship. These diamonds are then ranked on a 5-tiered scale from “Excellent” to “Poor”, based on these seven factors. Diamonds that rank “Excellent” will feature an even pattern of bright and dark areas, while diamonds lower on the scale will appear darker, with less “brightness” within them. Lower cut-quality diamonds will also have more undesirable proportions. 


But what about the shape of a stone? Isn’t that the cut?

Cut and shape are words that are often used interchangeably by many, but mean very different things. When the casual jewelry buyer thinks of cut, they often think about the shape or outline of the diamond, rather than the arrangement of its facets. Diamonds can come in many different shapes, the most popular being the round shape. All other outlines are known as “fancy shapes”, such as marquise, oval, and pear. I plan on going into more detail on the different shapes and how they affect a diamond’s quality in future posts. 

Why is cut important to quality?

When diamonds are being cut from raw material, the lapidary artist will have a few decisions to make. Not only do they need to choose a flattering shape for the diamond, but they also need to think about the proportions of the diamond as they cut. Many customers are willing to pay for larger, fair-cut diamonds over smaller, excellent-cut diamonds, putting pressure on cutters to sacrifice appearance in exchange for weight-retention. The Cut grade can be essentially to help a purchaser identify stones that were cut to maintain carat weight, as opposed to being cut for the best appearance of the stone. 

The way a diamond is cut will affect the way light is mirrored within the facets of a diamond. If a diamond is too shallow or too deep, the light will refract poorly and escape through the bottom of the diamond; this leads to the face-up appearance of the diamond being dark, and not having as much sparkle. Well-cut diamonds, on the other hand, will be proportioned so a majority of the light entering a diamond reflects back out the top of the diamond, creating lots of inner shine and brilliance. It is this brilliance that is highly prized in the diamond industry, as a sparkly diamond is the most desirable for many customers. 


How can I get the most out of my diamond’s cut?

When choosing a diamond, avoiding a poor cut is the primary concern, regardless of price or size. The most brilliant round diamonds, in the excellent and very good range, will be the most expensive, as they are the most desirable. You want to look for a diamond that ranks high in symmetry and polish, to fully experience the beauty of its cut. Fancy shaped diamonds allow for a little more wiggle room in terms of cut, as the shaping of the diamond can impact the reflection of light within the stone. It is important to choose both a flattering shape and a flattering cut for the diamond size that you wish to buy. 


What should I keep in mind about all 4Cs to get the very best diamond?

As with all things in life, picking the perfect diamond is all about balance and trade-offs. The very best diamonds will be large, flawless, colorless, brilliant…and very, very expensive. If you are looking for the best diamond you can find no matter the cost, great! You now have all the tools you need to find your perfect diamond. And for those balling on a budget, the best way to choose your diamond is to select with elements of the 4Cs you can’t live without. Are you looking for a large diamond? Or one that seems to shine from within? It all comes down to your personal style and preferences. By following the 4Cs and choosing the right combination for you, I have no doubt that you will find the perfect diamond for your forever jewelry!


Want to learn more? Check out these articles! 

From the GIA

More from the GIA

More about proportions