Heart Cut (Modified Brilliant Cut)
The complexity of the heart shape diamond requires a skilled cutter in order to ensure proper balance. As with other brilliants, proportions are most important in this cut. A shadow in the form of a bow-tie is also considered part of the beauty of this shape. Many jewelers make the mistake of attempting to select a diamond that doesn’t display the bow-tie. Since the outline needs to have a pleasing, obvious pear outline, symmetry is vital to this shape, and therefore, the lobes must be rounded and clearly defined. Ideally, the length to-width ratio should be slightly over .95:1; approximately 1:1 in favor of length, but not over 1.15:1. Keep in mind that one heart shaped diamond may exhibit a larger bow-tie effect than another, even though they both have the same weight and depth percentages due to variances in length-to-width ratios.
Diamond cutters and gemologists agree on a depth percentage between 58-65.4% as it delivers the greatest balance of fire and brilliance while exhibiting the smallest possible bow-tie effect. Depths under 58% usually produce larger bow-ties due to reduced pavilion angles while depths over 65.4% generally contain smaller bow-ties but appear darker and smaller overall.
Heart (Length-to-Width Ratio of 1:1)
Table               51-64%
Total Depth    58-65.4%