What are Ideal cut proportions?

[meepcat]

Hi folks,

I know WHAT these are, but I don''t know what they are for various carat sizes.

I''m specifically looking for what these are (with an Ideal, proportionate table length and depth -- AGS000, really) for:

1.5 carats
1.7 carats
2.05 carats
2.25 carats

Thank you so much!

 

[belle]

it''s the same for all of them

 

[valeria101]

The matter is reasonably well covered in the tutorial here...

Besides, there isn''t much need to learn them by heart or anything (there is a range of winning table & crown angle & pavilion angle combinations). You can check out the numbers from lab report using the Cut Adviser (under ''Tools'' on top of this page).

It might sound disappointing that there is no single ''Ideal'' - like two numbers to keep in mind. And while several grading labs have cut grades (GIA, AGS, EGL on some of their reports etc.), these ratings do not agree among themselves. And that''s one reason why I prefer to look at an independent evaluation of these cut grades - with HCA is. As far as I know, the standard used in the Cut Adviser shares some of the research base behind the cut grades by AGS... but has slightly distinct results. AGS0 graded diamonds would also come tops on the HCA.

There must be hundreds of posts about the matter - perhaps some may be relevant to your concerns as well.

Anyway, it may be easier to debate the merits of a couple of diamonds than theorize about the system - those are meant to be difficult, it looks like

 

[oldminer]

You can get sets of parameters for Ideal cut rounds in the AGA Cut Class charts. In rounds, 1A is pretty much the strict Tolkowsky parameters. 1B is still inside the AGS0 range. There are some not so wonderful AGS0 cut rounds on the outer edges of AGS0 that don'';t quite fit AGA 1B.

For fancy shapes, AGA has many of them defined, in traditional measures, but the new AGS 0 princess cut stands alone as non-traditionally cut. We now use ImaGem to define Ideal in Princess cut bsaed on light behavior. Its a bit of a mix-up as to which system to use and how to interpret who is correct. In time it will settle down.

 

[RockDoc]

RE: Variances in different size diamonds.


Next week is the AGS conclave meeting where some of this will be discussed, and hopefully when we return on May 1st we''ll have more definitive information.

In the Ideal range there charts that AGS supplied to many of us, the standard diameter of the stone is 6.mm

There are supposedly minor change in these parameters as the diameter changes, and we''ll have the details of that after the conclave.

AGS has done some very detailed scientific study of this and is educating of their results.


Rockdoc

 

[meepcat]

Also, can you provide me a link to the HCA, or other tutoral, where I can find the girdle diameter for the sizes I listed above?

 

[oldminer]

1.50ct= diameter squared x .6 diameter(the depth) x .0061
or
1.50 divided by .0061 divided by .6 =diameter to the third power.

If you take 7.4mm as the diameter and 60% of that as the depth and follow the formula
diameter squared x depth (7.4 x.6) x .0061, you'll end up with 1.48ct.....
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You can do the same for any size diamond with a simple calculator and some number substitution.

This approach assumes a "standard" 60% depth per the GIA formulas. You diamonds may have differing depths and therefore have differing diameters. Girdle thickness plays a big role, too.