Buyer’s Guide to Round Diamonds
Close your eyes and picture a diamond. You are picturing a round brilliant. This iconic diamond shape symbolizes millions of marriages, adorns millions of ears, and paves countless inches of gold.
What is the difference between a round diamond and a round brilliant diamond? While other kinds of round cut diamonds are technically possible, like a round rose cut diamond or an antique Old European cut, the modern round brilliant cut diamond is not only the most popular round cut diamond on the market, it’s the most popular diamond shape of all time.
The round brilliant diamond cut, with its 58 facets, pointed culet, and optimized proportions is the culmination of hundreds of years of perfecting the art of diamond cutting. Yes, the round brilliant cut is that good.
The History of Round Brilliant Diamonds
Diamond faceting began in the 15th century when it was first discovered that diamonds could be polished by their own dust. Before that, rough diamonds and polished crystals were the only way to wear this gem. Faceting unlocked the potential for sparkle. Once diamond cutters discovered the beauty of polished diamonds, they kept innovating, starting by polishing crystals, cutting off the top of the crystal to create a table diamond cut and then step cut diamonds. In the 16th century faceted diamond cutters developed rose cuts, followed by the cushion shape old mine cut.
Mazarins, the first brilliant cuts with more facets to maximize brilliance, were introduced in the middle of the 17th century. Then the industrial revolution in the late 19th century transformed diamond cutting. New steam-powered bruting machines and motorized saws allowed diamond cutters to create new diamond shapes that weren’t possible before: the round cut diamond was born. The Old European cut and English round cut had 58 facets, the same as round brilliant cut diamonds today.
In 1919, a young Belgian student studying match in London, Marcel Tolkowsky, wrote Diamond Design, his thesis on the ideal proportions for round brilliant cut diamonds. Although his study of the reflection of light in a round cut diamond omitted the girdle and needed to be adjusted, his work became the foundation for the modern round brilliant and the ideal proportions still prized today. Diamond cutters still use his research on crown angles, depth percentage and table percentage to maximize light reflection. Round cut diamonds today, which are cut for beauty instead of the largest possible carat weight, are the most brilliant gems possible thanks to modern technology.
Why We Love Round Diamonds
Brilliance. Fire. Sparkle. Nothing dances with light like a round brilliant cut diamond. These unrivalled optics are due to the symmetry and proportions that create optimum reflection, refraction, and scintillation. This diamond shape has the best light reflection of any diamond cut, with the most light that returns to the eye.
A round brilliant diamond in the sunlight will throw reflections and rainbows across the room.
The pure circular silhouette of the round cut diamond has inspired many ring styles, from the halo to the solitaire, and the three stone. That’s another reason why the round cut diamond is the most popular diamond shape for engagement rings.
The angles and proportions of round cut diamonds have been researched in depth by diamond grading laboratories and the cutting standards for the round brilliant are higher in general than for any other cut. The round brilliant cut is the only diamond shape with a cut grade on its GIA diamond grading report. Because GIA is the world’s most important diamond grading laboratory, it is very influential in the industry. Cutters know that diamonds with an excellent cut grade or very good cut grade from the GIA sell for more so they work hard to make sure their diamonds meet those high quality standards. That’s great news for you because it’s easier than ever to find a well-cut round diamond.
There’s one more reason why the round brilliant cut diamond is the most popular choice for engagement rings: it’s the most common cut so there is more choice available. You can select from thousands of options in every color, clarity, and carat weight. Every possible combination of the 4Cs of diamond quality is available in every carat weight.
There is one drawback to choosing a round brilliant diamond: high demand means that they are the most expensive diamond cut in most sizes. A round brilliant sells for more per carat than any fancy shape. It also looks smaller than many other fancy shapes a one carat diamond that’s round will look smaller than a one carat oval cut diamond, one carat marquise, one carat pear shaped diamond or one carat radiant cut diamond. The only diamond shape that looks smaller is the Asscher cut.
How to Buy Round Diamonds
The brilliance of most rounds makes them bright, so you don’t have to buy the top color grade to get a beautiful diamond. You also are less likely to see inclusions because of all that sparkle, so you don’t need to buy a flawless gem to have a beautiful diamond either. But what you definitely don't want to skimp on is cut: look for an excellent cut and your diamond will live up to the potential of the round brilliant cut diamond to dazzle with light reflection.
The best way to buy a round brilliant diamond is to buy it loose and then set it into a ring.
Buying a loose diamond will give you more control over its quality. Choose a diamond with a diamond grading report from GIA or AGS, the world’s most respected diamond grading laboratories, to make sure that the quality has been independently verified from an accurate and impartial third party.
If you choose a round diamond with an excellent cut grade from GIA, popularly known as an ideal cut, you’re sure to own a beautiful and well-crafted diamond. You can also buy diamond cut to an even higher standard: a round brilliant hearts and arrows diamond which demonstrates superior light performance when evaluated with a viewer that confirms the maximum amount of light is being returned back to your eye.
Make sure you buy your loose diamond from a company that demonstrates a commitment to responsible sourcing. Supporting the Kimberley Process is a great start but the best suppliers go beyond that, sourcing diamonds directly from sightholders and mines.
What ROSI Recommends
When you are shopping online for a round brilliant diamond, there are thousands and thousands available: too many for anyone to individually review one by one. That’s why we created ROSI, an artificial intelligence personal shopping tool powered by IBM’s Watson: to sort through all the round brilliant diamonds available on the market to find the best balance of quality and value for your budget. Thanks to ROSI, you can find the best round brilliant diamond for your budget in one single step.
ROSI generally recommends a diamond color grade of H and clarity grade of VS2 for round diamonds. This will give you a diamond that looks colorless with no inclusions visible to the naked eye. If your budget is limited, an eye-clean SI1 diamond is also a good choice. The money you save can be invested in a larger size diamond and a better cut. ROSI recommends excellent cut, symmetry and polish for a round diamond that sparkles beautifully. ROSI also recommends ideal cut diamonds and hearts and arrows diamonds, which do cost more but will have maximum brilliance.
Round Brilliant Quality Checklist
- Color: H
- Clarity: VS2
- Cut: Excellent
- Symmetry: Excellent
- Polish: Excellent
- Depth: 58%-63%
- Table: 53%-62%
- Fluorescence: None to Faint
- Comments: No chips!
There’s one final step to making sure that you’ve found the right round brilliant diamond. No matter where you found your diamond, you can compare your diamond by putting the GIA report number into ROSI. In a few seconds, you’ll see if artificial intelligence can find you a better diamond value. You may find a higher-rated diamond at the same price or a similar stone for a lower price. If not and your diamond passes the A.I. Challenge, you know you are really getting a great deal.
Round Brilliant vs Oval Shape Diamonds vs Cushion Cut Diamonds
The two diamond shapes that are most similar to a round brilliant diamond are the oval shape diamond and the cushion cut diamond.
The oval shape diamond is less brilliant than the round brilliant but its elongated silhouette and shallower depth means it looks much larger on your finger than a round brilliant the same weight. In addition, oval shapes sell for less per carat for the same quality and size.
Cushion cut diamonds are similar in size to the round brilliant and are the only other diamond cut that will display the hearts and arrows pattern in a light-performance viewer. A hearts-and-arrows cushion like RockHer’s Cushion Brilliant designed by master cutter Brian Gavin, is a great way to get the precision cutting and high light performance of a hearts and arrows cut for less per carat than a hearts and arrows round brilliant.
Best Round Diamond Engagement Ring Styles
Our customers’ favorite setting for round diamonds is a simple solitaire diamond band engagement ring. Delicate micropave halo engagement rings are also popular. Recently, we’ve seen more brides interested in unique halo engagement rings that have a more custom look. Simple diamond solitaire engagement rings are an eternal classic that never goes out of style, just like the round brilliant. Popular three stone styles feature three round diamonds or round with tapered baguettes on the side.