It is easy to assess the quality of the shape of brilliant cut diamonds. Brilliant cut diamonds should be… well, round! Most brilliant cut diamonds, especially those with excellent or very good cut grades, are very round, or at least so round that no variation can be detected with the naked eye.
For fancy-cut diamonds, things get more complex. They don’t get cut grades from GIA, because there is such a wide variety of cut shapes and styles, each with their own length-to-width ratios and a set of standards. Personal preferences also play an important role.
Here are 4 things to watch out for in Diamond Fancy Shapes
1. Length-to-width ratio: The L-W ratio is the ratio of the length to the width of a patterned shape, with the width expressed as number one. Most people find some relationships more attractive than others. For example, emerald cuts, rectangular cushion cuts and pears are most popular in L / W ratios between “1.50 / 1” and “1.75 / 1”.
L / W ratios are also important because buds that are too long and narrow tend to break.
2. Symmetry of the line: For hearts and pears, the outline of the diamond should be the same on both sides when you draw a line in the center. For ovals, squares, rectangular cuts and marquises, the outline of the diamond must be the same on each side vertically and horizontally. Symmetry makes a diamond crisp and clean and helps maximize the brilliance of a diamond. The GIA grading report of a fancy cut diamond does not contain a cut grade, but it does indicate the symmetry and polish of the stone.
3. Soft curves: Curved shapes such as hearts, pears and ovals must have full and rounded “lobes” or “shoulders”. The curves should flow smoothly and have no hard-looking flat spots.
4. Defined shape: It should be obvious what the shape of a diamond is. A heart, for example, should have a defined slot and a pointed opposite point. The attractiveness of the shape of a diamond can sometimes depend on the relationship. An oval with too low a length-to-width ratio may appear to be an uneven round.