4 replies to this topic

[JamesB]

The diamond (an Infinity diamond):

 - 1.011 cts. Princess Cut (Square Modified Brilliant)
 - G VVS2
 - AGS 0 cut (Ideal)
 - Ideal Polish/Symmetry/Light Performance
 - 5.41 x 5.39 square
 - Dimensions:
	Table:  61.1%
	Total Depth:  78.3%
	Crown Height:  10.9%
	Pavilion Depth:  64.0%
	Girdle:  Thin to Medium
	Crown Angle:  32.7°
	Pavilion Angle:  42.1°

Pricescope (and other sites) cite Tables of 62 - 68% and Depths of 64 - 75% as 'Ideal Cut' proportions... but I frequently see diamonds above 75% depths or with tables as small as 56% that have been given an AGS0 'Ideal Cut' rating.

The dealer is assuring me that the diamonds are cut for light performance, and I believe him, it's a beautiful diamond. Paul Slegers suspects that AGS has quietly lowered the minimum level of the ideal grade.

So my question is, is it reasonable to consider the diamond above, with a slightly higher depth and slightly smaller table than 'ideal' proportions, an AGS0 Ideal Cut?

Thanks!
James

[denverappraiser]

JamesB, on 19 June 2011 - 02:13 PM, said:

The diamond (an Infinity diamond):

 - 1.011 cts. Princess Cut (Square Modified Brilliant)
 - G VVS2
 - AGS 0 cut (Ideal)
 - Ideal Polish/Symmetry/Light Performance
 - 5.41 x 5.39 square
 - Dimensions:
	Table:  61.1%
	Total Depth:  78.3%
	Crown Height:  10.9%
	Pavilion Depth:  64.0%
	Girdle:  Thin to Medium
	Crown Angle:  32.7°
	Pavilion Angle:  42.1°

Pricescope (and other sites) cite Tables of 62 - 68% and Depths of 64 - 75% as 'Ideal Cut' proportions... but I frequently see diamonds above 75% depths or with tables as small as 56% that have been given an AGS0 'Ideal Cut' rating.

The dealer is assuring me that the diamonds are cut for light performance, and I believe him, it's a beautiful diamond. Paul Slegers suspects that AGS has quietly lowered the minimum level of the ideal grade.

So my question is, is it reasonable to consider the diamond above, with a slightly higher depth and slightly smaller table than 'ideal' proportions, an AGS0 Ideal Cut?

Thanks!
James

Table and depth aren't the AGS criteria for evaluating light performance and never have been. In the case of princess cuts, total depth percentage isn't even one of the variables used. The rules are complicated, and I'm not aware of any changes recently but I suppose it's possible. I'll ask. I'm an AGS member and titleholder and they should be pretty forthcoming about it.

Edited by denverappraiser, 20 June 2011 - 07:29 AM.

[davidelevi]

Interesting situation.

On the one hand, you have tables quoting ranges based on heuristic and observation, but no systematic research (and frankly, in the case of many if not most fancy shapes, providing useless if not outright dangerous information).

On the other, you have AGS who after extensive research looks at the diamond, makes a 3D ray-tracing model of it and decides it fits its characteristics for the highest cut grade. Which BTW is the only researched definition of "Ideal" cut - all the rest is somebody's opinion not supplemented by science.

On the third hand (gripping hand, anyone?), you have the cutter of the diamond (Paul Slegers owns Infinity) who says that AGS may have slipped on standards. Yet it is AGS that is evaluating one of his stones, and is saying it comes out tops - completely disregarding its depth.

Unsurprisingly, you are confused.

Neil will settle the AGS standards question; I will point out a couple of other things:

1. Infinity does cut princesses in a very individual way - very deep and with high crowns. Some people like the fire and life that this brings to the stone, others find the impact on other aspects of the stone is excessive.

2. The one definite effect that high depth has is to make the diamond smaller compared to others - by as much as 0.3 mm in this case, so it's definitely visible.

If you like the cut, don't mind the effect it has on the size, and are OK with the price, I would not let the question of whether it fits within tables that have no value other than guidelines (if that) stand in your way.

[denverappraiser]

The AGS parameters for cut grading of princess cuts have not changed, nor is AGS Lab applying them differently than they were a few years ago.

Infinity uses a set of rules that's a bit more specific than AGS's, meaning that all Infinity's are AGS-0's but not all AGS-0's would fit into their product line. Perhaps this subset is what Paul was talking about as having changed.

[jan]

JamesB, on 19 June 2011 - 02:13 PM, said:

The diamond (an Infinity diamond):

 - 1.011 cts. Princess Cut (Square Modified Brilliant)
 - G VVS2
 - AGS 0 cut (Ideal)
 - Ideal Polish/Symmetry/Light Performance
 - 5.41 x 5.39 square
 - Dimensions:
	Table:  61.1%
	Total Depth:  78.3%
	Crown Height:  10.9%
	Pavilion Depth:  64.0%
	Girdle:  Thin to Medium
	Crown Angle:  32.7°
	Pavilion Angle:  42.1°

Pricescope (and other sites) cite Tables of 62 - 68% and Depths of 64 - 75% as 'Ideal Cut' proportions... but I frequently see diamonds above 75% depths or with tables as small as 56% that have been given an AGS0 'Ideal Cut' rating.

The dealer is assuring me that the diamonds are cut for light performance, and I believe him, it's a beautiful diamond. Paul Slegers suspects that AGS has quietly lowered the minimum level of the ideal grade.

So my question is, is it reasonable to consider the diamond above, with a slightly higher depth and slightly smaller table than 'ideal' proportions, an AGS0 Ideal Cut?

Thanks!
James

You can.... but keep in mind that stones of higher depth look smaller for the carat weight. Personally I like to keep our 1.00 ct. diamonds 74 or lower on princess cut.