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By  , Wednesday, August 23, 2006


Diamond CutCut is the most important aspect of diamond beauty.  It is the only factor controlled by man, but for many years it has been the least discussed.  Here you will learn what details have the most impact on a diamond’s beauty and more importantly, how to FIND this information.








Diamond proportions 


The Importance of Cut Grading


Cut refers to more than just a diamond’s shape.  It refers to more than depth, table, polish and symmetry.  A round diamond’s cut quality also depends on physical measurements called proportions.  A diamond’s proportions determine how well a diamond will sparkle and reflect light.  There are 11 different proportions and cut details for a round diamond.






These details are all necessary for determining a diamond’s quality, but many sellers still provide only 7 of them. 




Cut quality is the most important information about a diamond, but in many places you will no mention of the missing proportions or a grade for cut.  The most common grading labs used by diamond sellers provide some details on cut proportions, but not enough to determine cut quality. 


Notice in the example below that there are grades for color and clarity, but not for cut.  Without the missing details a diamond cannot be properly evaluated and cannot be measured against already-established cut grades.





Lack of consumer awareness


Most consumers don’t realize there are grades for cut.  Color and clarity have been graded since the 1930s but no major lab graded cut until 1996.  Most diamonds on the world market would not qualify for a top grade, so cut grading has been met with resistance in some places.  Since cut is the only C that man controls, you may wonder why most diamonds are produced at an average level of quality.




Why most cut quality is average


It takes planning and effort to transform a piece of rough into a polished diamond.  The greater the planning and effort, the more beautiful the diamond will be.  However, more effort causes more rough material to be polished away, resulting in less carat weight. 




For many years consumers were unaware of the importance of cut, so it was cost-effective for factories to produce diamonds of average quality since they could be finished more rapidly and retain more carat weight.  As education about diamond cut has spread on the internet, the demand for higher quality increases and factories are improving their methods.  Still, to this day only a small number of diamonds are cut to premium quality.  



Laboratories responding to consumer demand


The good news is that factories and laboratories are responding to consumer demand.  As of 2006 two of the world’s most reputable labs are providing all details and assigning cut grades for round diamonds.  These labs are the American Gem Society and the Gemological Institute of America.  AGS and GIA grading reports give parameters necessary to determine cut quality.




Note:  GIA reports several details as rounded numbers so an independent Sarin or Helium report is recommended to accompany a GIA-graded diamond, in order to know all proportions measurements with greater accuracy.


The Pyramid of Cut


The AGS and GIA approach cut grading differently, but both are proven systems.  Diamonds awarded the top grade by these labs are near the top of what we call the pyramid of cut.




The AGS system is very strict.  Less than 3% of the world’s round diamonds can earn the AGS top grade of 0 or ‘Ideal.’   The GIA’s top grade of ‘Excellent’ allows for a range of taste that is broader but is still an assurance of good quality.


A diamond earning one of these grades is above average cut quality and, very importantly, will have passed all tests for depth, durability, polish and basic symmetry.  It will also have visibly superior performance compared to average diamonds. 


The AGS Ideal grade is considered very elite.  The GIA Excellent grade has more latitude and allows abundant steep/deep combinations (so GIA EX diamonds may appear smaller than they should for carat weight), but the information is provided so you can assess this for yourself.


Our Strong Opinion


We encourage buyers to seek diamonds graded by the AGS or GIA.  They provide detailed cut information and the reputability and strictness of these labs with color and clarity grades allows diamonds accompanied by their paperwork to retain better value.  A top grade from the AGS or GIA is the best assurance of quality offered by any major lab.


Cut Information Summary


Consumers know very little about cut because most of the world’s diamonds are still graded by labs that do not offer a cut grade.  A person doesn’t need to know every last number to make a good decision, but understanding cut grading allows a more informed and confident decision.


>>Next: Cut Analysis


For more specific questions ask our experts
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