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Diamond Cut Grade Quality: All of the aspects of a diamond’s proportions contribute to a diamond’s cut quality. |
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Pic: Screenshot of OctoNus software |
The quality of a diamond’s cut is the only property that should be dependent on the viewer. Although often overlooked, cut is probably “the” most important aspect to consider when choosing your diamond. What makes judging cut difficult is that beauty is in the eye of the beholder; different people perceive the beauty in different ways.
GIA even admits that “The information contained in [the] GIA Web site is not a substitute for the analytical or appraisal services of a credentialed jeweler or gemologist. Prior to purchasing any particular diamond or piece of jewelry, the user should consult with a credentialed jeweler or gemologist about the importance and interrelationship of cut, color, clarity, and carat weight.”
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For more on GIA’s parameters see: http://www.fireandicediamond.comresearch/1383/2313/article_detail.cfm
The word "cut" actually refers to two different traits of a diamond:
1) the shape: round, princess, radiant, emerald, pear, heart, oval, marquise
2) the cut grade: how well the shape is cut, including proportions, finish, and symmetry.
Light should enter a diamond through the table and crown without being reflected off the surface. The light should be reflected off the diamond’s inside and refracted or dispersed, and travel back out throughout the top at the speed of light. This refraction causes colors to separate and creates a diamond’s fire. The white light return is a diamond’s brilliance. We like to think of this as the ice. The movement of light is called scintillation. The color and clarity of the diamond also affects this light return. Inclusions may absorb some colors in the spectrum and blur others. Fissures or cracks in the diamond will change the specific gravity and return of light. Graining in a diamond’s polish also interferes with the lights absorption and return. The carat weight may mean that a set of proportions that work at one weight will not work at others.
Cut is much more difficult to “visualize” and therefore, although the single most important determinant of a diamond’s beauty, is the least understood. The blame for this long accepted ignorance lies within retailers who have relied on salespeople rather than gemologists to show diamonds to the public. As the educational efforts of De Beers are resulting in an industry-wide class of trained gemologists, cut grade is beginning to be properly represented and is finally gaining support as the single most important aspect of a diamond’s beauty.
There are so many qualitative variables within diamond proportions that make a diamond cut desirable and so many factors that affect light’s behavior and little agreement on what constitutes beauty in a quantifiable manner, making cut grade implausible to quantify. GIA has maintained this until market pressure by AGS, Moscow State University, OctoNus, Garry Holloway, and about a hundred others forced them to grade cut. Until recently, gemologists have always looked at a combination of a diamond’s overall brilliance or white light return, fire or colored light, and scintillation - the flashes of light seen when the diamond moves. The initial cut grade research they conducted focused on Round Brilliant diamond shapes, but grading laboratories like AGA and AGS are slowly introducing cut grades for the fancy shapes like the princess, emerald, oval, radiant, cushion and others. Each diamond shape has its own set of cut parameters that produce the optimal light performance and beauty for that particular diamond shape.
Pic: Pricescope.com
In manufacturing a diamond, a diamond cutter will analyze a rough diamond and determine how to extract the most beauty and most profit out of the rough crystal. A poor cut combined with many inclusions can make an actual diamond worthless no matter what the size.
AGS began documenting their “ideal” or 0 cut grade in 1996 using light performance, proportions, and finish through several computer models as the technology was evolving. Following AGS’s lead, GIA now bases their Excellent cut grade on measurements on almost the same computer model. Unfortunately, neither have actual people visually evaluate the diamonds because of subjectivity and time constraints.
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Here is an example of a 2ct Round Brilliant cut diamond, F color and VS2 clarity with very good polish. This was passed on to a retail jewelry store because of the poor selection of their wholesaler at one time.
Notice how the surface of the diamond acts like a mirror reflecting light directly off it before the light can even enter the diamond. This is a result of inferior symmetry and cut. |
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This is an example of a 2ct H color VS2 clarity Round Brilliant cut diamond with very good symmetry. A wholesaler may have selected this diamond under a search based on the Four C’s and, on the Rapaport Wholesale Price Sheet; they may have believed that it was a good investment. Notice how light enters the diamond, but isn’t able to be refracted and travel back out. In fact, you can see the setting through the top of the diamond. This is a result of a combination of both an inferior polish and cut. |
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GIA New Cut Grading Scale
It is extremely important to learn about the cut grade of a diamond for three reasons:
1) the cut varies greatly from one diamond to another
2) the cut grade determines over 80% of the beauty of a diamond
3) a concise grade for the cut is not included on most diamond certificates prior to 2007, including the GIA Diamond Grading Report. AGS, GIA, EGL, and AGA are now the only recognized lab that does give a cut grade and provides extensive details about the cut and proportions. Ask yourself the following questions to find out which category you would place yourself.
Perfection: If you want perfection regardless of cost - start by looking at brand-name Super Ideal Cut round brilliants, like Hearts on Fire, SuperbCert, or our Distinct Diamonds. It used to be that you wanted a diamond to show the famous "hearts and arrows" pattern under special viewers to be sure you are getting the top cuts, but now we see a lot of other cutters that can create diamonds with beauty that rivals or matches the overall brilliance and fire of the hearts and arrows stones, but do not necessarily show this pattern. Ask your Fire and Ice Diamond Consultant and continue reading for more details. Branded diamonds sell for quite a premium, so expect to pay perhaps 20-30% more for that luxury.
Excellent Quality: If you want quality and beauty for a lot less money; ask for an Ideal Cut. This is not the same as the hearts and arrows and they are not cut by brand name cutters that have spent millions to promote their names and logos, but they usually show a good combination of brilliance and fire.
Large and Beautiful: If you want a larger stone without sacrificing beauty, ask for an Excellent cut (called a Premium Cut at most places these days). These will give you a good balance of beauty but at a greatly reduced price. This is what the Fire and Ice Diamond staff recommends to most people.
Large and Nice: If you want a larger stone for your money, ask for a Good to Very Good cut grade, usually a 2 cut grade on an AGS certificate. These are still beautiful and more brilliant than any other natural gemstone. If cut goes below this, you sacrifice too much, but these are still nice enough for a special engagement ring.
Largest: Even if you are mainly concerned about getting the largest size, we do not recommend Fair to Poor cu grades for engagement rings. They have a noticeable lack of brilliance and fire (even when color and clarity are very high). In our opinion, such diamonds are fine for regular decorative jewelry, but not appropriate for an engagement ring.
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