Diamonds - Cut

The cut of a diamond has a tremendous impact on its final brilliance, fire, and sparkle. Numerous studies have been conducted to determine the ideal cut for a stone. Many variations of cut have been tried, from changing the number of facets to changing the angles of the crown and pavilion, to changing the proportions of the size of table (the top of the stone).

Although opinions of what constitutes “ideal” or “premium” cut proportions vary depending on the source, there are certain ranges that are generally considered to provide the most desirable fire and brilliance from a stone. These ranges cause the light entering the diamond to be reflected back through the table (top), not through the sides or bottom.

In addition to the significant difference in brilliance and light return there is a difference in the face up appearance of cut variation in diamonds. Shallow stones have a larger total diameter, so they appear bigger which may seem like an advantage, but the loss of brilliance is not desirable. Deep stones will have a smaller diameter for their size and will not look as big or “face up” as comparable stones of the same weight.

Historically, round diamonds have been the most popular and most widely available shape of diamond. Because of this, researchers have spent most of their time and energy on perfecting the angles and percentages that should appear in a round stone.

Although other diamond shapes follow many of the same principles, the ranges are wider and the percentages are different. These shapes (any shape other than round) need to be evaluated on overall beauty and on whether the shape is pleasing to the eye. See the descriptions under shape for more information. As illustrated in the chart above, there is a range of proportions that will provide excellent brilliance and fire. Diamonds that fall within the top three categories above will result in a beautiful diamond that will sparkle in any light.

Polish:
Polish represents the detail work in the cutting process. The polish grade describes how well the cutter was able to bring out the luster or shine in the facets. It also relates to the smoothness of the diamond's facets. With poor polish, the surface of a facet can be dull, and may create blurred or lackluster sparkle.

Symmetry:
The symmetry grade refers to alignment of the facets. If you imagine the crown facets as windows and the pavilion facets as mirrors, symmetry relates to how well they are lined up. If the angles and the alignment are not exact, the amount of light being returned by the pavilion facets (mirrors) will be drastically reduced.

Summary:
For the past few years, the Gemological Institute of America (GIA) has been working on an industry wide review of the accepted standards of cut. While the final results have not been published, basic information has been released. The conclusions seem to point to several distinct combinations of table and depth proportions that result in equally brilliant diamonds. These combinations are a departure from having only one standard range of ideal cut that was acceptable in the past. Anyone who has graded a significant number of diamonds has come across many beautiful diamonds with incredible brilliance that do not conform to those earlier standards of cut.

Our Take:
We hope you just read the paragraph immediately above this, because it points the new direction our industry is going, which is a departure from the rigid parameters of the traditional ideal cut and embracing the acceptable variances of premium and good cuts. In keeping with that, we prefer diamonds with slightly larger tables because the table is the window we look through to see into the diamond. In general, we favor a table percentage between 57% and 64% which includes the Very Good, and Good categories.