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Cut

The cut of a diamond — its roundness, its depth and width, the uniformity of the facets — all determine a diamond's brilliance. Many gemologists consider cut the most important diamond characteristic because even if a diamond has perfect color and clarity, a diamond with a poor cut will have dulled brilliance.

The width and depth have the greatest effect on how light travels within the diamond, and how it exits in the form of brilliance.

Too Shallow: Light is lost out the bottom causing the diamond to lose brilliance.

Too Deep: Light escapes out the sides causing the diamond to appear dark and dull.

Cut determains Brilliance
The diamond's proportions, specifically the depth compared to the diameter, and the diameter of the table compared to the diameter of the diamond, determine how well light will reflect and refract within the diamond.

Diamond Anatomy

Polish and Symmetry Affect Sparkle

Polish and symmetry are two important aspects of the cutting process. The polish grade describes the smoothness of the diamond's facets, and the symmetry grade refers to alignment of the facets. With poor polish, the surface of a facet can be dulled, and may create blurred or dulled sparkle. With poor symmetry, light can be misdirected as it enters and exits the diamond. The polish and symmetry grades are clearly listed in each diamond detail page and within the AGSL or GIA diamond grading report. For the most beautiful diamond, look for a symmetry grade of ideal (ID), excellent (EX), very good (VG), or good (G) for an AGSL graded diamond, and excellent (EX), very good (VG), or good (G) for a GIA graded diamond. Avoid diamonds with symmetry grades of fair (F) or poor (P), as the alignment of their facets may misdirect light so severely that it affects the brilliance of the diamond.

Diamond measurements are calculated and applied to a cut grading scale that makes it easy to understand how well each reflect light:

• Blue Nile Signature Ideal cut: Represents roughly the top 1% of diamond quality based on cut. The highest grades of polish and symmetry allow it to reflect even more light than the standard ideal cut. Our most brilliant cut.
• Ideal cut: Represents roughly the top 3% of diamond quality based on cut. Reflects nearly all light that enters the diamond. An exquisite and rare cut.
• Very good cut: Represents roughly the top 15% of diamond quality based on cut. Reflects nearly as much light as the ideal cut, but for a lower price.
• Good cut: Represents roughly the top 25% of diamond quality based on cut. Reflects most light that enters. Much less expensive than a very good cut.
• Fair cut: Represents roughly the top 35% of diamond quality based on cut. Still a quality diamond, but a fair cut will not be as brilliant as a good cut.
• Poor cut: This includes all diamonds that do not meet the proportion standards of a fair cut. These diamonds are deep and narrow or shallow and wide and tend to lose most of the light out the sides and bottom. Blue Nile does not carry diamonds with cut grades of poor.

Blue Nile Diamond Cut
Blue Nile carries the largest selection of ideal cut diamonds. You'll find no diamonds with cut grades lower than fair, which are too shallow or deep to present an acceptable amount of brilliance.

Which Cut Grade is Best?
For a diamond with the best cut, that will look exceptional even when viewed under a microscope, look to the Blue Nile Signature Collection. These diamonds reflect the most brilliance because they are cut to the most exacting proportions, and have the highest polish and symmetry grades for round diamonds, and have either excellent or very good for princess-cut, emerald-cut, and Asscher-cut diamonds.

For the best value in a brilliant diamond, choose a diamond with a cut grade of good or very good, and polish and symmetry grades of very good or good.

In an ideal- or very-good cut diamond with very good or good polish and symmetry, consider less expensive grades of color and clarity — look for a diamond with G or H color and SI1 or SI2 clarity.