Author Topic: Class 1, 2, 3 and 4...  (Read 2752 times)

Offline Rubymu

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Class 1, 2, 3 and 4...
« on: May 19, 2008, 11:47:20 PM »
I've just heard about GIA apparently giving class distinctions to diamonds - class 1 through 4.  Class 1 is apparently 'investment quality' and so on down the list.

Does this sound right?  It was something I read recently online, and it just didn't ring true to me. 

Offline Mikla

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Re: Class 1, 2, 3 and 4...
« Reply #1 on: May 20, 2008, 07:14:13 AM »
Dear Rubymu -

I looked it up and here's what I found:

GIA Make Classes

CLASS                     1                              2                             3*                                        4**   
TABLE                  53-60%***             61 - 64%                65 - 70%                                 +70%   
CROWN               34-35                     32 - 34                 30 - 32                                   -30   
GIRDLE     medium to slightly thick   thin to thick    very thin to very thick   extremely thin to extremely thick   
PAVILION              43%                       42 - 44%                41 - 46%                             -41 / +46%   
CULET           none to medium         slightly large                 large                                 very large   
FINISH     very good to excellent         good                          fair                                      poor   

* Class 3 also includes stones with 51 or 52% tables or 37 crown angles.
**Class 4 also includes stones with tables less than 51%, crown angles more than 37 , or major symmetry variations.
***Table size for Class 1 goes up to 61 to 62% in stones under 0.50 ct.
_____________________________________________________________________________________

Class 1: The cutting precision of what we might call Class 1 stones strikes the trained eye immediately. The impression is one of a harmonious balance between both the various physical dimensions and components of optical display -brilliance, fire, and scintillation. Stones in this class required extra time and care to produce a high-quality finish, so they normally cost more.Generally, in sizes from about 0.50 carat up to be considered Class 1, stones must have table sizes from 53 to 60 percent, crown angles from 34 to 35 , even girdles that are medium to slightly thick, pavilion depths very close to 43 percent, small to medium culets(or undamaged), and very good to excellent polish and symmetry. In smaller sizes, slightly larger tables - up to about 62 percent - are acceptable, but the other criteria are the same.

Class 2: These stones are very attractive, with minor variations which few customers and trained or experienced jewelers would recognize. These stones have table sizes from 61 to 64 percent, crown angles from 32 to 36 , thin or thick girdles, pavilion depths from 42 to 44 percent, small to slightly large culets, and good polish and symmetry.

Class 3: Many of these stones have been stretched to push them into higher weight categories. An example of stretching would be a large table and shallow crown that were cut to obtain a stone weighing a little over one carat.
Class 3 stones have table sizes from 65 to 70 percent, crown angles from 30 to 32 , very thin or very thick girdles, pavilion depths from 41 to 46 percent, large culets, and fair polish and symmetry.

Class 4: Class 4 stones have such variations that even the untrained observers sense that something is amiss, even if they can not say exactly what it is.Class 4 are stones with table sizes larger than 70 percent, crown angles shallower than 30 , extremely thin or extremely thick girdles, pavilion depths shallower than 41 percent or deeper than 46 percent, very large culets, poor finish, and major symmetry variations.
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Offline Trinkette

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Re: Class 1, 2, 3 and 4...
« Reply #2 on: May 20, 2008, 10:18:44 AM »
Hum. I hadn't heard about this.  Must go see. BTW, I assume that we're talking only about rounds...

Offline Diamondsbylauren

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Re: Class 1, 2, 3 and 4...
« Reply #3 on: May 20, 2008, 01:31:49 PM »
HI Everyone!

I just checked with our GIA contacts- what Mikla posted isnot information published by GIA, rather it's someone's idea about how to classify the cut ( make) of diamonds with GIA reports.

Basically, the chart is useless.
I believe it's an old chart- since 2006, GIA has classified the cut of round diamonds ( not using this chart either)
David
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Offline Diamondsbylauren

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Re: Class 1, 2, 3 and 4...
« Reply #4 on: May 20, 2008, 03:57:52 PM »
Further clarification:

In fact, the chart listed WAS included in a GIA publication from 1994. There was never any discussion of actually implimenting the chart as a "standard" - it was more like guidelines.


Once GIA started work on actually grading the cut of round diamonds, they did not use the stats on this chart.
Still, great detective work on the part of Rubymu, and Mikla in finding this stuff!!
Bravo!!
David
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Offline Trinkette

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Re: Class 1, 2, 3 and 4...
« Reply #5 on: May 21, 2008, 09:22:43 AM »
Rubymu, this was a great question.  Thank you Mikla and David for doing the legwork! It is kind of interesting to see how GIA was thinking, regardless whether or not they actually followed through with the plan.