The round brilliant cut diamond is one of the most popular and most researched diamond shape available today, representing approximately 75% of all diamonds sold. Due to the mechanics of its shape, some believe the round diamond has an advantage over other diamond shapes at the proper reflection of light, maximizing potential brightness. For almost 100 years, diamond cutters have been using advanced theories of light behavior and precise mathematical calculations to optimize the fire and brilliance in a round diamond. In addition to being the most popular and researched shape, a round diamond may give you more flexibility in terms of balancing cut, color, and clarity grades while still getting the fire and brilliance you want.

The Princess cut has increasingly become the second most popular cut shape for diamonds, next to a round brilliant. Its beautiful brilliance and unique cut makes it a favorite for engagement rings (and also for earrings). The princess has pointed corners and is traditionally square in shape. The princess cut is a relatively new diamond cut, having been created in the 1960s. It has gained in popularity in recent years as a more distinctive alternative to the more popular round brilliant cut. A princess cut with the same width as the diameter of a round brilliant will weigh more as it has four corners which would otherwise have been cut off and rounded to form a round brilliant. 

The square princess cut diamond is usually slightly cheaper than round brilliant cut diamonds of the same carat weight because it retains about 80% of the rough diamond, as opposed to the round brilliant which retains only about 50% of the rough. The ability to retain more crystal weight makes this shape popular amongst diamond cutters.

The unique look of the emerald cut diamond is created by the step cuts of its  and its large, open table. Instead of the sparkle of a brilliant-cut, emerald cut diamonds produce a hall-of-mirrors effect, with the interplay of light and dark planes. While some say the emerald cut is less fiery, the long lines and dramatic flashes of light give the emerald cut an undeniable elegant appeal. The shape was originally developed for the cutting of emeralds, thus the name. What makes this shape different is its pavilion, which is cut with rectangular facets to create a unique optical appearance. Due to its larger, open table, this shape highlights the clarity of a diamond. If you choose an emerald-cut with a lower clarity grade, such as SI, be sure to review the clarity plot on the diamond certificate. Emerald-cut diamonds can vary greatly in how rectangular they are. If you'd prefer an emerald cut with a squared outline, you may also want to look at an Asscher-cut diamond. 

The asscher cut diamond was first produced in 1902 by the Asscher Brothers of Holland, famous at the time for cutting the world's largest rough stone (the Cullinan, at 3,106 carats). This beautifully unique shape is nearly identical to the emerald-cut, except that it is square. 

Asscher cut diamonds originally peaked in popularity in the 1920's, and could recently be found only in antique jewelry shops. Around 2002, one hundred years after the first asscher cut diamond was created, the shape began to make a comeback, spurred on by cut modifications that gave the shape more brilliance than traditional asscher cut diamonds.

The modern asscher cut diamond is similar to a square emerald cut, usually with larger step facets, a higher crown, and a smaller table. This combination often produces more brilliance than the emerald cut. A well cut asscher will appear to have concentric squares as you look down through the table, the result of proper positioning of the pavilion facets underneath. Like the emerald cut, the asscher cut has cropped corners; however, because an asscher is square, the cropped corners give the asscher cut a somewhat octagonal shape. Once mounted in a four prong setting, the diamond maintains its unique shape within a square silhouette.

The football-shaped marquise diamonds are a modified brilliant-cut. The name is derived from the Marquise of Pompadour, for whom King Louis XIV of France allegedly had a stone fashioned to resemble what he considered her perfectly shaped mouth. Because marquise diamonds are long and narrow, they can also create the illusion of greater size. Carat for carat, the marquise diamond has one of the largest crown surface areas of any diamond shape, making it a good choice when trying to maximize the perceived size of a diamond. Like the oval diamond, the marquise cut diamond's elongated shape can make the finger of the wearer appear longer and slimmer. This brilliant-cut diamond looks beautiful set with round or pear-shaped side stones, and the length of the marquise makes fingers appear long and slender. 

Created by Lazare Kaplan in the 1960's, oval diamonds are a modified brilliant-cut (like virtually all round cuts). Because the two shapes possess a similar fire and brilliance, the oval is an ideal choice for a customer who likes the look of a round diamond, but wants something more unique. Oval diamonds have the added advantage of an elongated shape, which can create the illusion of greater size. The slender shape can also make the finger of the wearer appear longer and slimmer, an effect often desired. Oval diamonds are also very popular as their length can accentuate long, slender fingers.

The radiant cut diamond is the first square cut (the second being the princess) to have a complete brilliant-cut facet pattern applied to both the crown and pavilion, creating a vibrant and lively square diamond. First popular in the 1980's, the cropped corner square shape of the radiant is a nice bridge between a cushion and a princess cut, and for that reason looks beautiful set with both rounded or square cornered diamonds.Trimmed corners are the signature of this diamond, and they help make the radiant-cut a popular and versatile choice for jewelry. A radiant-cut looks equally beautiful set with either baguette or round side-diamonds. 

The modified brilliant-cut pear shaped diamond is a combination of a round and a marquise shape, with a tapered point on one end. The diamond is always worn with the narrow end pointing toward the hand of the wearer. Like marquise and oval cuts, the pear shaped diamond comes in a variety of slim to wide cuts, and has the added benefit of making the wearer's fingers appear longer and slimmer.This brilliant-cut diamond is also called a teardrop for its single point and rounded end. The unique look of the pear shape helps make it a popular choice for a variety of diamond jewelry. If you choose an elongated pear shape, the length of the diamond creates a subtle slimming effect on the fingers.

The modified brilliant-cut heart shaped diamond is a unique and unmistakable symbol of love. Heart shaped diamonds are very popular in solitaire pendants as well as rings. When choosing a heart, symmetry is a very important characteristic, since it is critical that the two halves of the heart are identical. The cleft (between the two lobes) should be sharp and distinct, and the wings (the sides as they curve down to the point) should have a very slightly rounded shape. The heart is the ultimate symbol of love. The unique look of the heart-shaped diamond helps make it a distinctive choice for a variety of diamond jewelry.

The cushion cut diamond  combines a square cut with rounded corners, much like a pillow (hence the name). This classic cut has been around for almost 200 years, and for the first century of its existence was the most popular diamond shape (similar to round cut today)! Until the early 20th century, the cushion cut diamond was the de facto diamond shape.This unique shape has been popular for more than a century. Cushion-cut diamonds (or "pillow-cut" diamonds) have rounded corners and larger facets to increase their brilliance.