This is your mission, should you choose to accept it: purchase diamonds with the quality your customers demand at a price point that meets your budget. Impossible? No. When buying diamonds, just make sure you are equipped with the right information -- from the right sources! One of these critical pieces of intel is cut grades. Here’s what you need to know:

Understanding Diamond Cut | K. Rosengart

The Most Important C

Pear, emerald, oval, round… these all refer to a diamond’s shape. Cut is a different animal. It has more impact on the appearance and value of a stone than any of the other Cs (i.e. clarity, color, and carat). A stellar cut optimizes brilliance, fire, and scintillation. This is why meticulous diamond cutting executed by expert hands is so crucial.

When you purchase a stone, your source should supply certification from an independent grading agency, such as GIA. Now, when these grading labs rate a diamond’s cut, they look at three factors:


If you loved geometry, you’re in luck: proportions are all about angles. The facets of the crown allow light to enter the stone; the facets of the pavilion reflect that light back through the crown facets to the viewer. To allow optimal interaction of light, the facets must be cut at just the right angles in relation to each other: e.g. a steeper pavilion facets would be balanced by shallower crown facets and vice versa. Rather than looking at individual facets, look at how they “work” together. For example, if light hits the pavilion facet at 45°, ideally, it leaves the facet at 45°.

When you purchase diamonds, GIA will send a cut grade report that includes a proportion diagram. It shows you information such as the size of the girdle and culet, table and depth percentages, and crown and pavilion angles.

Diamond Cut Grades | K. Rosengart

Image from GIA



Nature is remarkably symmetrical; the mathematical precision you find in a nautilus shell, the spiralized seeds of a sunflower, and the equidistant radial supports of a spider’s web is astonishing -- and perfect. In the hands of an expert cutter, diamonds also boast marvelous symmetry.


Let’s look at a round brilliant diamond: symmetry is achieved when:

  • The main facets of the crown and pavilion are positioned 45° relative to each other.
  • The upper and lower girdle facets are positioned 22.5° relative to each other and 11.25° to their mains.
  • The star facets are 45° from each other and 22.5° from the crown facets.
  • All facets in a facet group are identical in size.
  • Facet groups are the same distance from the table.
  • The table should be parallel to the girdle and star facets should be of equal length.


When the stone is not symmetrical, it interferes with the facet angles. This, in turn, impacts the appearance of a diamond.


Proper polishing enhances the diamond’s ability to reflect light. A diamond that has top rated proportions and symmetry is only ⅔ of the way to an exceptional stone. Polish is the third piece of the pie. During the diamond cutting and polishing process, craftspeople can leave microscopic defects, such as marks from the polishing wheel. If severe enough, these marks can interfere the play of light -- and thus, the diamond’s value.


An “Excellent” rating means that the diamond has no defects visible at 10x magnification. “Poor” means that defects are visible to the naked eye. Avoid “Poor.” These stones are not worth your investment or time. However, if your diamond is 0.75ct or less, a grade of Fair or better is perfectly acceptable; it won’t impact the appearance of the stone. As well, if you have visible inclusions, you can opt for a grade of Fair or above.


It is helpful to understand the anatomy of a diamond so you can see how all these factors coalesce to create maximum impact. If you have any questions about cut grades -- or anything else -- feel free to ask our expert team.

Melee Diamond Buying Guide | K. Rosengart