Diamond Cut
As the single human contribution to a polished diamond's beauty, cut is perhaps the most important, yet most over-looked, of the Four Cs of diamond quality. How does cut affect a diamond's value and beauty? A good cut gives a diamond its brilliance, its dispersion, its scintillation-in short, its life. And brilliance is what a diamond is all about, especially in the eyes of the consumer.
The particular angles and finish of any diamond are what determine its ability to handle light, which leads to brilliance. Several factors need to be considered:
Proportion:
A well-cut diamond reflects light back to the eye evenly in the face-up position, with no dark areas. Dark or 'dead' areas are due to poor cutting, and should not be confused with the faint "bow-ties" which are typical of fancy shapes; in the case of fancy shapes, bow-ties are where the main brilliance and life of the diamond are most apparent.
As you can see from the illustrations, when a diamond is well-cut (either a fine cut or an Ideal cut), light enters through the table and travels all the way to the pavilion where it reflects from one side to the other - intensifying in the mirror-like facets as it travels - before reflecting back out of the diamond through the table and to the observer's eye.
In a poorly cut diamond, however, the light that enters through the table reaches the pavilion facets and then 'leaks' out from the sides or bottom of the diamond rather than reflecting back to the eye.
Identify a jeweler who has invested in the latest technology for grading diamond proportions. Prior to mounting a diamond should be graded on a Sarin Diamension proportion grading machine.
The Sarin DiaMension proportion analyzer provides the most accurate evaluation of diamond proportion measurements available today. It is used by GIA, American Gem Society (AGS) and other gemological laboratories to analyze diamond proportions.
If a merchant selling diamonds cannot provide you with a Sarin report then BUYER BEWARE!
A sample output from a Sarin Proportion grading machine is shown here. View a sample Sarin Diamond Grade Report (DGR).
Finish:
Finish refers to the qualities imparted to a diamond by the skill of the diamond cutter. The term "finish" covers every aspect of a diamond's appearance that is not a result of the diamond's inherent nature when it comes out of the ground. The execution of the diamond's design, the precision of its cutting details, and the quality of its polish are all a consideration when a gemologist is grading finish. If you examine a diamond's grading report, you will see its finish graded according to two separate categories: polish and symmetry.
POLISH refers to any blemishes on the surface of the diamond which are not significant enough to affect the clarity grade of the diamond. Examples of blemishes that might be considered as 'polish' characteristics are faint polishing lines and small surface nicks or scratches.
SYMMETRY refers to variations in a diamond's symmetry. The small variations can include misalignment of facets or facets that fail to point correctly to the girdle (this misalignment is completely undetectable to the naked eye).
Major symmetry problems are often seen in diamonds graded as Fair or Poor; they can include severe misalignment of facets, a noticeably off-center table, a noticeably 'wavy' girdle, or a table which is noticeably not parallel to the girdle. However, these types of problems are not a consideration when buying a diamond from a reputable jeweler. Your jeweler should be able to answer all your questions without hesitatation and provide you with a Sarin diamond report along with any other cerifications from GIA or AGS.
LEARN MORE:
Basic 4Cs | Diamond Color | Diamond Clarity | Diamond Cut | Diamond Carat | Beyond the 4Cs | Diamond Brilliance | Ideal Cut Diamonds | Diamond Grading Systems