A Complete Guide to Diamond Cut

When a diamond catches your eye, you will probably notice its sparkle first. There is only one factor that contributes to the twinkle of a gem: diamond cut.

But before diving into all things diamond cut, understanding the anatomy of a diamond is critical—and jeweler Tanya Parikh has the perfect analogy by comparing diamonds to a slice of pizza. "Picture this! The crust is your crown. The girdle is the thin area that attaches the top to bottom, and the cheese is the pavilion of the diamond," she describes to Brides. "In relation to the crust and cheese ratio, the crown and pavilion of a diamond must be proportional to allow for that great light return and sparkle."

She adds, “If the proportions are correct, the light—even in the most dimly lit room—will play inside the stone and come back to the eye in the form of sparkle. That sparkle and fire in a diamond are what makes it very attractive.”

A diamond can have gorgeous color, flawless clarity, and a large carat weight, yet still be unattractive and undesirable—making cut the most important component of the 4Cs. Ahead, Parikh shares everything you need to know about diamond cut, from the grading scale to the best cuts to choose.

Grading Scale

There are two main components that determine the quality of a diamond cut. “The first is the actual material that is being cut. Being a natural product, diamond rough material will vary from stone to stone. That being combined with the skills of a master cutter will unlock the life in the stone and give it its cut quality.”

The cut of a round brilliant diamond (and only a round brilliant diamond) is then given one of five gradings: excellent, very good, good, fair, and poor.

• Excellent: These diamonds are pristinely cut with the correct proportions to maximize the fire, sparkle, and brilliance in the diamond.
• Very Good: Diamonds with this grade are beautifully cut. They are very similar to excellent-grade diamonds, although slightly less quality.
• Good: These diamonds are cut in such a way that gives some sparkle to the stone, but may be disproportionate in some areas. Because of these inconsistencies, Parikh cautions that she would never sell a diamond with a good cut grade for an engagement ring. 
• Fair: Light easily exits through the bottom and sides of a fair grade diamond. For this reason, fair cut diamonds are not ideal for center stones but could be suitable for smaller side stones on a ring.
• Poor: As the name of this rating suggests, poor cut diamonds are the least favorable—and luckily, the least common. Parikh shares, “As a diamond dealer for over a decade I do not think I have ever seen a diamond with a poor cut grade. Often times the poor cut grades can be found in small melee diamonds that are non-certified because no grade is better than a bad grade!”

Types of Cuts

"The uniqueness of a diamond comes from the individual angles or facets of a diamond," explains Parikh. "There are multiple ways to facet a diamond, including a brilliant cut, step cut, rose cut, single cut, and more. These terms describe the placement of the facets which model the stone to sparkle in the way it ultimately does."

Brilliant Cut

With a brilliant-cut diamond, the majority of the facets are all angled towards each other, creating a kaleidoscope effect and a burst of sparkle. With a well-cut, brilliant-cut diamond, it is easy for its inclusions and diamond hue to be masked.

Step Cut

On a step-cut diamond, the majority of the facets are angled parallel to one another. This creates a stunning window into the diamond. Step-cut diamonds are typically very high in clarity because any inclusions are noticeable without magnification. 

Shopping Advice

While shopping for an engagement or wedding ring, Parikh recommends having a very high threshold for cut tolerance. She explains, “If you go lower on the cut grade, it will take away from the life of the diamond.”

She also cautions couples to not let diamond shape overshadow the stone's cut. “In my opinion, the biggest mistake that clients make when buying a certain diamond cut is only recognizing the shape and not the proportions of the diamond. Often times, especially with online purchases, that can be lost in translation and a well-priced stone gets sold with a good, fair, or poor cut grade.”