Find your diamond
Find your jewelry
shape
carat
color
clarity

Cut Classes on grading chart

Status
Not open for further replies. Please create a new topic or request for this thread to be opened.

zoebartlett

Super_Ideal_Rock
Joined
Dec 29, 2006
Messages
12,450
Could someone please explain the different classes in grading -- 1A, 1B (American Ideal Cut), 2A, 2B (International Fine Trade Cut), 3A, 3B (US Domestic Average Cut)? I''m assuming it''s best to stick with depths, percentages, angles, etc. listed in the class 1 category. An explanation would be great though. Thanks!
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
Messages
6,378
The AGA Cut Class charts are based on the Tolkowsky concept of parametric screening to determine the best to worst range of cutting parameters. All parametric systems roughly translate into screening categories relative to the light performance of most diamonds. What we find with modern equipment or computation, is that rough parameters only do a rough job. More direct analysis or more computational analysis leads to a finer tuned result. This clearly is a logical situation. With more knowledge and advancements in technology, we get more repeatable and dependable results.

The AGA Cut Class is a well tried system and can prove useful for screening out stones that don''t perform so well, but as time has progressed, I see more diamonds with rather low cut quality which still perform nicely in their light behavior. What does this tell me? It tells me that cutters are getting better at their craft due to advancements in predictive software which leads them to be able to cut prettier diamonds even with unusual or non-traditional parameters. So long as Durability, Finish and Size(spread) are not problematic, I have no real problem with new cut parameters which my old system does not predict well for. BUT, I do now utilize the DFS system to highlight "problematic" parameters which may impact in a negative way on Durability, Finish or Size of a given diamond.

The AGA Cut Classes were in use long before predictive tools or direct measurement tools came into the market. 1A is a very narrow Tolkowsky set of parameters for round diamonds. 1B is still within the modern version of Tolkowsky for round diamonds. 1A and 1B are both tight parameters within the old AGS 0 range for rounds. It is my experienced interpretation for all the fancy shaped diamonds that is graded 1A to 4B. There is no Tolkowsky or traditional based system for fancy shapes, so I have gone alone into the marketplace although after all these years, no one has done better, so it seems. AGS 0 princess cuts are very pretty, but generally quite deep for their weight, resulting in a rather small looking but very beautiful stone for their weight. Both the AGA Cut Class and the DFS system tend to downgrade them for over depth. However, the DFS is only used with a direct measurement of light technology which generally rates AGS 0 diamonds as Very Good or Excellent in terms of their light behavior. We separate DFS from Light Behavior and provide individual scores of each component. 1 part is beauty and 1 part is craftsmanship, I suppose.

I hope this assists you in understanding the complex issues that are involved. The entire process was made to assist people to know more, and make the process less blind. It was never intended to be totally understood except by a few curious experts.
 

Unearthed

Shiny_Rock
Joined
Feb 14, 2007
Messages
103
The stone I purchased falls within 1a specs on everything but the crown angle, which is 35. This would place that spec (And the entire diamond?) into the class 1b area. It does however, score below a 2 on the HCA and is nearly blinding in the correct light. I would think a diamond that has good specs, falls within the 1a-1b range, and scores well on the HCA would be a nearly sure fire bet to be a real sparkler...regardless if the result of one "Test" is barely out of the range that we consider to be "Ideal."
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
Messages
6,378
You are probably correct, but there are people who are looking to buy an ultimate stone, not a great one. I never know which sort of person is addressing these issues. A diamond which scores an AGA 1B and 2 on the HCA is going to be a beautiful diamond. Wiull it be the best one ever? Who knows, or who cares? Admittedly, there are people who want exactly what others don''t care at all about.

In the end, there is no general answer without seeing the diamond. Always buy what you prefer and seek advice when you don''t know or can''t understand.
 
Status
Not open for further replies. Please create a new topic or request for this thread to be opened.
Be a part of the community It's free, join today!
    Three-stone engagement ring upgrade
    Three-stone engagement ring upgrade
    Vintage OEC Bracelet
    Vintage OEC Bracelet
    June’s Birthstone Trinity
    June’s Birthstone Trinity

Need Something Special?

Get a quote from multiple trusted and vetted jewelers.

Holloway Cut Advisor



Diamond Eye Candy

Click to view full-size image.
Top