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Home >> Diamond Grading >> Diamond Shapes >> Oval Shape >> Depth %


Specific proportions regarding the ideal depth of an oval shape diamond have not been conclusively determined or published by Gemological Institute of America. Ideal proportion is more difficult to establish in an oval shape 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. An oval diamond has a pavilion that is made up of a variety of angles due to variance in length and width. (See Diagram)
Oval Shape Diamond Cut Guide
Specifications for Ideal to Very Fine Cut

Select Emerald Cut Diamonds Within These Ranges

     total depth % ---------- 62% - 68%

     table % ---------------- 50% - 62%

     girdle thickness ---------Very Thin - Thick

     cullet ------------------ None - Medium

     polish ------------------ Excellent - good

     symmetry -------------- Excellent - Good

     flourescence ----------- None - Faint

     Length to width ratio --- 1.3 - 1.7 to 1

The depth percentage of an oval shape diamond is determined by dividing the diameter measurement by the depth measurement. Diameter is determined by measuring an oval diamonds width from side to side. The longer length measurement is not taken into consideration when calculating diameter. By viewing an oval shape diamond from the end view 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 an oval shape diamond due to shallower pavilion angles that run towards its pointed long end.

An oval 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 affect in the center of the diamond. The bow tie affect is a result of a small amount of light leaking through the diamond.

The diagram illustrates a variety of oval shapes with bow tie affects showing resulting changes in appearance due to differing depth percentages and length to width ratios. The bow tie affect when seen in an actual oval shape shape 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 affect 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 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 vary 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 an oval shape diamond with a depth percentage between 63% and 68% delivers the greatest amount of brilliance while exhibiting only a small bow tie affect. Oval shape diamonds under 62% usually produce larger bow tie affects due to reduced pavilion angles. Oval shape diamonds which measure over 68% generally have less bow tie but appear darker and smaller overall.

When choosing your diamond be aware of its length to width ratio. Keep in mind that one oval shape diamond may exhibit a larger bow tie affect than another oval shape diamond 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 an oval shape diamond's width. Therefore, a longer one carat oval shape 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 oval shape diamond with a length of 5 millimeters and a width of 4.6 millimeter with an equal depth percentage of 65% would have a deeper total depth of 2.9 millimeters. Oval shape diamonds of shorter length and greater width display a smaller bow tie affect 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 oval shape diamonds. Our Certified Gemologist-Appraisers will be happy to help guide you to the most brilliant oval shape diamond your money can buy.

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