Diamonds come in a variety of shapes. Do not confuse cut with shape, cut is what determines how well-cut your diamond is, whereas diamond shape is the shape it was cut into.
Round Brilliant Cut:
The round cut diamond is the most popular diamond shape, representing approximately 75% of all diamonds sold. Due to the mechanics of its shape, the round diamond is generally superior to fancy diamond shapes at the proper reflection of light, maximizing potential brightness.
Virtually all round diamonds are brilliant-cut, meaning they have 57facets. The demand for round diamonds is very high, and the yield is relatively low. Because more of the rough stone is lost in the cutting of a round diamond, the cost of each carat retained is higher.
Oval cut 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.
A square cut diamond that has refractive properties almost near round brilliant. The princess is the preferred square cut shape over radiant. The princess cut diamond is the most popular fancy cut, especially for engagement rings. Like round cut diamonds, princess cut diamonds are a good choice for their flexibility in working in almost any style of ring.
A more traditional shape is in squire or rectangle shape with eight angles. The emerald is not as popular as it used as it once was, but has old world elegance to it. The unique look of the emerald cut diamond is created by the step cuts of its pavilion 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 less fiery, the long lines and dramatic flashes of light give the emerald cut an elegant appeal. The shape was originally developed for the cutting of emeralds, thus the name
Emerald cut diamonds varies from nearly square to a narrow rectangle. The classic emerald cut diamond has a length to width ratio of around 1.50. If you prefer the look of the square emerald cut diamond, be sure to consider the asscher cut as well (which has a very similar appearance, and is defined by GIA as a square cut emerald). Every Lumera Diamond includes precise measurements, as well as the length to width ratio, so you know the exact shape of the emerald cut diamond you are considering
Popular before the princess shape was around; the radiant has more facets than a princess, but has the corners trimmed like the emerald shape. This shape is not widely popular. The radiant cut diamond is the first square cut 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.
The cushion cut diamond once referred to as old mine cut) 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.
Traditional cushion cut diamonds return light in a chunkier pattern than modern cuts. Combined with the enlarged culet (which was considered desirable for the pattern created when viewed through the table), this created a distinctive look that is prized today among dealers in antique diamonds.
Partially based on cut research initiated by Marcel Tolkowsky in the 1920's, refinements to cushion cut diamonds over time, have led to resurgence in popularity. Many buyers are attracted to the antique feel combined with modern performance offered by the cushion cut.
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.
Heart shaped diamonds of less than .50 carats may not be a good choice, as the heart shape is more difficult to perceive in smaller diamonds, especially after they are set in prongs. For smaller hearts, a bezel or three prong setting (one prong on each lobe, one prong at the point) will better preserve the heart shape outline of the diamond after it is set.
A diamond or gemstone that is cut in a modification of the brilliant cut so that the girdle is boat-shaped with a hexagonal table surrounded on the crown by 32 trapezium shaped and triangular facets. Like the emerald, the marquise is a traditional shape. This is probably the fourth most popular shape behind the round, princess and oval. 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.
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.
Ideally, a pear shaped diamond should possess excellent or very good symmetry. The point should line up with the apex of the rounded end. The shoulders and wings (the upper and lower curves on the right and left side of the diamond) should form uniform, symmetrical curves, with no straight edges. The rounded top should not appear narrow or squat, but like a semi-circle. In a misguided effort to add weight to a diamond (by incorporating more of the rough stone in the final cut) cutters may give the diamond added girth near the point or top, giving the diamond a squared off or squatty appearance.
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.