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| Diamond Cut |
Many people confuse diamond cut with the shape of a diamond. Unlike shape, diamond cut is the metric used to evaluate the precision and quality of the overall cutting itself. Diamond cut is the most complex of the 4 Cs, and not even the major labs agree on how to best measure the quality of a diamond’s cut. Diamond Cut usually takes into consideration 3 criteria: Proportions, Symmetry and Polish. Sometimes Light Performance or other tests can be used to also calculate the precision of the diamond cut.
| 1. When a diamond is cut to proper proportions, light is reflected from one facet to another and then dispersed through the top of the stone similar to the image shown to the left. |
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| 2. If the cut of the diamond is too deep, some light escapes through the opposite side of the pavilion. |
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| 3. If the cut is too shallow, light escapes through the pavilion before it can be reflected. |
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Up until several years ago, evaluating the cut of a diamond was not an easy task. Dimensions and proportions of the diamond as well as its finish (both symmetry and polish) were all the information able to be evaluated, thereby making it difficult for consumers to understand what is a well-cut diamond and what is not.
Symmetry measures how well the facets match the other facets. A diamond cut with very good or excellent symmetry means that if you were to look at all the facets and compare to one another, they would look very uniform with very little variance. This doesn't mean however the diamond is not cut too deep or too shallow.
Polish is a measure of the surface finish. If a diamond is only polished "Fair" or "Good" it does not allow maximum transition of light through the facets, due to it's "rough" surface texture. Very Good polish by most lab standards is usually sufficient to get the top cut grade, and excellent/ideal is often preferred. Polish graded above Very Good is not detectible to the naked eye.
So while symmetry and polish help you determine if the diamond is cut well, it doesn’t always mean the diamond will perform like a well cut diamond.
Recently both the GIA and AGS have adopted “Cut Grades” which factor all these things together; the proportions, symmetry and polish, and sometimes even light performance. Currently, GIA issues a cut grade on its round diamonds, and AGS issues a cut grade on round and princess shape diamonds they grade.
We often recommend consumers consider at least a GIA Very Good or Excellent Cut grade diamond if considering round or princess shapes. For those who want to be assured of a top cut, there is also the coveted AGS Triple Zero grade which they claim to be the best ideal cut achievable. It's hard to go wrong with either an AGS Ideal grade or GIA Excellent grade stone.
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Questions? Ask our Diamond Experts and other Members in our Diamond Forum |
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