A Guide to Round Cut Diamonds

When shopping for the perfect diamond, there are lots of things to consider. What is the quality of the stone? What setting do you prefer? What shape will be the most flattering for that setting? Each shape and quality diamond will have different pros and cons, and knowing the basics will help you to make the perfect decision for you, and, perhaps, your partner. 

There are twelve basic shapes that are used to cut gems in the jewelry industry: Princess, Emerald, Cushion, Asscher, Pear, Oval, Heart, Radiant, Marquise, Baguette, Trillion, and Round. Each of these shapes comes with a different set of qualities that determine the price, quality, and overall appeal of the diamond. This series of blog posts will include a deep dive into each of these shapes, and help you to determine which shape is right for you and your ring. 

The Round Cut Diamond

Of all the diamonds being bought and sold in the industry, three-quarters of all these stones are round cut. It is one of the most used shapes in all engagement rings, desired for its brilliance and inner fire. This seemingly simple shape allows for this diamond to boast the most facets of any cut, 58 total facets giving the round cut stone a sparkle unlike any other. These diamonds reflect light extraordinarily well, which is highly favored in a ring as visible as an engagement ring. 

The modern round cut diamond shape looks vastly different from vintage cut stones. One of the earliest versions of the round brilliant cut was developed in the late 1800s, and is now known as the “Old Mine Cut”. This term was used to identify that the stone was mined in either Brazil or India, and was cut in a distinctly squarish shape, to enhance the sparkle in the stone. Another version of the round cut diamond is now referred to as the “Old European Cut”. This diamond shape is known for its large facets, cut to preserve carat weight rather than for brilliance. As both of these old style stones are no longer being produced, in favor of the modern round cut, they are prized for their rarity and the craft that went into making them, as cutters did not have the modern technology to rely on when cutting. 

The modern round brilliant cut was developed in 1919, when Marcel Tolkowsky published his thesis on diamond design, creating a mathematical formula for cutting diamonds proportionally. Advances in technology have allowed cutters to perfect this formula, so they no longer have to rely on eyeballing a diamond’s proportions.

What Do You Mean by “Brilliant Cut”?

The brilliant cut of a diamond refers to a certain pattern of facets and proportions that impart exceptional brilliance to a diamond. The shape of a brilliant cut diamond allows a cone of light to pass through the stone, bouncing around inside the facets and creating a gorgeous sparkling pattern. The modern brilliant cut enables a mosaic of light and dark patterns to be reflected in it in a star shape, while older brilliant cuts, such as the Old European and Old Mine cut, create a more checkerboard look. 

This all accomplished through different proportions of the fifty-eight facets that make up the brilliant cut. While a diamond is made up of many distinct parts, there are a few sections that are most important to determining the brilliance of the cut, particularly the crown, pavilion, and table facets. Different angles and sizes for these facets will lead to a different quality of brilliance. If a diamond has a large table facet, but is shallow in depth, the light will pass through the bottom of the stone without reflecting back and creating the signature brilliance of this cut. A deep diamond with a small table will cause the light to bounce out the sides of the diamond, again missing the mark on brilliance. Ideal diamonds will be well proportioned in terms of table width and total depth, reflecting both white and colored light almost flawlessly. The most aesthetic diamonds will have a length to depth ratio between 1.01 and 1.03


Why is This Shape So Popular? 

Aside from the brilliant sparkle of a round brilliant cut diamond, these diamonds possess a classic, timeless look. This diamond is complemented by many different settings and styles, capable of being set in a simple modern setting or a vintage engagement ring. This is a shape of stone that can be passed down for generations, or easily remade into something new. 

How Do I Pick the Perfect Setting for my Round Cut Diamond? 

Because the round brilliant cut is so popular for engagement rings, it pairs well with many different types of setting. The most popular setting for this is the solitaire, or 4 prong, setting. Simple and elegant, this setting allows for a lot of light to enter into the gemstone, letting it sparkle to maximum potential. Round diamonds are also an excellent choice if you want a setting with a diamond halo, adding an extra pop of sparkle to your stone. Adding pave diamonds, or experimenting with the shank can also add to the elegance of your ring. In the end, going with your gut and choosing a setting that appeals to you will be the best way to go. 

Want to learn more about round cut diamonds? Check out these articles. 

An In-depth Guide to Round Diamonds

History of the Round Brilliant Cut

On Ideal Diamond Proportions

From the GIA: Diamond Anatomy

From the GIA: The Brilliant Cut

The Old Mine Cut

The Old European Cut 

Read Our In-Depth Series of Posts on Diamond Quality

Carat Weight