Marquise Depth Percentage
Specific proportions regarding the ideal depth of a marquise cut diamond have not been conclusively determined or published by Gemological Institute of America. Ideal proportion is more difficult to establish in a marquise cut diamond than it is in a round diamond. A round diamond has a consistent pavilion angle that makes ideal proportions easier to establish as a depth percentage. A marquise diamond has a pavilion that is made up of a variety of angles due to variance in length and width. (See Diagram)
The depth percentage of a marquise cut diamond is determined by dividing the diameter measurement by the depth measurement. Diameter is determined by measuring a marquise diamonds width from side to side. The longer length measurement is not taken into consideration when calculating diameter. By viewing a marquise cut diamond from the end you can see how similar it looks to the proportions of a round diamond. When you view it from the side you can easily see how the pavilion angle is altered due to its longer length. A small amount of light refracts through the pavilion of a marquise cut diamond due to shallower pavilion angles that run towards its pointed long end.
A marquise diamond has a uniquely beautiful shape that is favored by many women, but a small percentage of brilliance will be sacrificed for the beauty of this unique diamond shape. This brilliance loss is most often seen as a bow tie effect in the center of the diamond. The bow tie effect is a result of a small amount of light leaking through the diamond.
The diagram illustrates a variety of marquise cuts with bow tie effects resulting in changes in appearance due to differing depth percentages and length to width ratios. The bow tie affect when seen in an actual marquise cut diamond will be significantly more difficult to recognize than is illustrated in this diagram. This diagram serves only as a guide to approximate bow tie size. The bow tie effect is never as clear and distinct as shown in this diagram. It is usually seen as a shadow made up of white and dark reflections.
Gemologist and diamond cutters agree that a small bow tie effect is considered part of the beauty of this unique and beautiful diamond shape. Many people make the mistake of attempting to select a diamond which displays no bow tie. This type diamond will typically have a very deep pavilion which gives the diamond a slightly darker appearance within the entire table facet . This diamond will also be small in size compared to better proportioned diamonds of equal carat weight. Diamond cutters and gemologists agree a marquise cut diamond with a depth percentage between 63% and 68% delivers the greatest amount of brilliance while exhibiting only a small bow tie effect. Marquise cut diamonds under 62% usually produce larger bow tie affects due to reduced pavilion angles. Marquise cut diamonds which measure over 68% generally have less bow tie effect but appear darker and smaller overall.
When choosing your diamond be aware of its length to width ratio. Keep in mind that one marquise cut diamond may exhibit a larger bow tie effect than another marquise cut diamonds even though they both have a the same identical weight and depth percentages. This is due to variances in length to width ratios. Depth percentage is a percentage of a marquise cut diamond's width. Therefore, a longer one carat marquise cut diamond which has a length of 6 millimeters and a width of 4 millimeters and has a 65% depth percentage would have a total depth of 2.6 millimeters. A shorter one carat marquise cut diamond with a length of 5 millimeters and a width of 4.6 millimeters with an equal depth percentage of 65% would have a deeper total depth of 2.9 millimeters. Marquise cut diamonds of shorter length and greater width display a smaller bow tie effect due to resulting steeper pavilion angles. It is precisely these variances that make it more difficult to establish a simple measure for identifying ideally proportioned marquise cut diamonds. Our Certified Gemologist-Appraisers will be happy to help guide you to the most brilliant marquise cut diamond your money can buy.