ASET vs AGA Cut Class

[tenniz23]

I found a princess cut diamond that looks very promising. Its ASET image looks pretty good (at least to my amateur eyes) with good symmetry and a good amount of red. However, when I plugged in the diamond's dimensions and proportions into the AGA Cut Class Grader and compared to the AGA Princess Cut Chart, the diamond was graded as 3A:

Table: 1B
Crown Height: 1A
Girdle: 3A
Depth: 1A
Polish: 1A
Symmetry: 1A
Grade: 3A

It seems that this is based mainly on the Girdle component of the grade since the diamond has a Thick - Very Thick girdle. My understanding of AGA Cut grading is that it is a tool meant for narrowing the selection pool by rejecting badly proportioned diamonds. I always thought this meant that a high AGA grade doesn't guarantee high performance (i.e. a diamond that has poor light performance can still get a 1A grade). Is the opposite also true? Does a low AGA grade guarantee poor performance? Worded another way, is it possible for a diamond to receive a low AGA grade despite performing well?

What is your recommendation for this particular diamond? Is it a buy or no buy? For your reference, here are the GIA report, ASET image, and Sarin report for the diamond I'm considering:

 

[diamondseeker2006]

I think you can use the charts to just help you steer in the right direction. The ASET is very helpful in knowing more about the light performance of the stone than the measurements can tell you. I think that stone looks okay in the ASET, but I wouldn't want a table that large. The thick girdle can result in the stone having a face up diameter that is smaller than it should be. It is on the deep side, too. I'd be more inclined to look at ideal cut princess stones, or at least use them as a comparison to help you get the best GIA stone that you can. The first stone I linked is only 1.5 cts but it is 6.36x6.34mm which isn't but a little smaller than the 1.67 you are looking at. Plus it is more square.

Examples:

http://www.whiteflash.com/loose-diamonds/princess-cut-loose-diamond-2941432.htm

http://www.whiteflash.com/loose-diamonds/princess-cut-loose-diamond-2948342.htm

This 1.5 ideal cut is also about the same size as the one you linked.

http://www.whiteflash.com/loose-diamonds/princess-cut-loose-diamond-2957768.htm

 

[Christina...]

You may find this information pertaining to the AGA more helpful. It's also interesting to note that many AGS0 princess cuts score around 2A 2B on the AGA, but are very beautiful stones.

http://datlas.com/do-it-yourself-aganaja-cut-class-grader/

I think DS made some beautiful recommendations as well.

 

[tenniz23]

I think you can use the charts to just help you steer in the right direction. The ASET is very helpful in knowing more about the light performance of the stone than the measurements can tell you. I think that stone looks okay in the ASET, but I wouldn't want a table that large. The thick girdle can result in the stone having a face up diameter that is smaller than it should be. It is on the deep side, too. I'd be more inclined to look at ideal cut princess stones, or at least use them as a comparison to help you get the best GIA stone that you can. The first stone I linked is only 1.5 cts but it is 6.36x6.34mm which isn't but a little smaller than the 1.67 you are looking at. Plus it is more square.

Examples:

http://www.whiteflash.com/loose-diamonds/princess-cut-loose-diamond-2941432.htm

http://www.whiteflash.com/loose-diamonds/princess-cut-loose-diamond-2948342.htm

This 1.5 ideal cut is also about the same size as the one you linked.

http://www.whiteflash.com/loose-diamonds/princess-cut-loose-diamond-2957768.htm

Thanks for the recommendations, but I know for a fact that my girlfriend has a number in her mind about the carat size she wants and it's 1.70. The Whiteflash ACA diamonds are indeed very beautiful, but they are simply out of my budget (except for that first one although it has a dark spot in its center).

As for the girdle thickness of the diamond I posted, is the primary downside that it makes for a smaller-looking diamond? Are there any other downsides that I'm not thinking of? On the flip side, does the thicker girdle make it less prone to chipping?

 

[oldminer]

The AGA Cut Class grader was developed well before any AGSL lab came into being and before there was an effort to perfect the AGS000 princess cut. The AGS 000 princess cut is definitely a very attractive stone, but it is cut a particular way somewhat differently than what had been the norm of cutting princess cut diamonds when I was working on this system. I have often stated that it is not really possible to use the AGA Cut Class grader to match the AGS000 princess cut grade, but have said that once you have an AGS000 princess, your worries about cut quality issues are over, so you don't need to screen further.

The AGA tool is a way to screen non[/b-] AGS000 princess cuts, those which do not seek to meet the AGS cut style that has become their well respected Brand of princess cut diamond. There are hundreds of times more regular cut princess stones than those AGS has graded, many of which are worthy of consideration, especially by those people who are not the total perfectionist, those who are not necessarily into a "brand", or those who want to shop far more broadly for a "best" overall deal rather then totally go for the premium branded products.

You would be extremely hard pressed to find a 1A , 1B or 2A princess cut but they do exist and I think they likely have merit in cut and appearance, but it is a screening situation and you need to look and decide if it works on a particular diamond.

 

[Christina...]

The AGA Cut Class grader was developed well before any AGSL lab came into being and before there was an effort to perfect the AGS000 princess cut. The AGS 000 princess cut is definitely a very attractive stone, but it is cut a particular way somewhat differently than what had been the norm of cutting princess cut diamonds when I was working on this system. I have often stated that it is not really possible to use the AGA Cut Class grader to match the AGS000 princess cut grade, but have said that once you have an AGS000 princess, your worries about cut quality issues are over, so you don't need to screen further.

The AGA tool is a way to screen non[/b-] AGS000 princess cuts, those which do not seek to meet the AGS cut style that has become their well respected Brand of princess cut diamond. There are hundreds of times more regular cut princess stones than those AGS has graded, many of which are worthy of consideration, especially by those people who are not the total perfectionist, those who are not necessarily into a "brand", or those who want to shop far more broadly for a "best" overall deal rather then totally go for the premium branded products.

You would be extremely hard pressed to find a 1A , 1B or 2A princess cut but they do exist and I think they likely have merit in cut and appearance, but it is a screening situation and you need to look and decide if it works on a particular diamond.

Thank you for the clarity Dave! I hope that you didn't feel that my comment was in anyway an effort to discredit the AGA, I only meant to re-state what I had seen you write in regard to the scoring of AGS0 princess cuts and the AGA. In hindsight I should have included the link, https://www.pricescope.com/tools/AGA_NAJA_Cut_Class_Grader so that the OP could have read it in it's entirety.

 

[tenniz23]

The AGA Cut Class grader was developed well before any AGSL lab came into being and before there was an effort to perfect the AGS000 princess cut. The AGS 000 princess cut is definitely a very attractive stone, but it is cut a particular way somewhat differently than what had been the norm of cutting princess cut diamonds when I was working on this system. I have often stated that it is not really possible to use the AGA Cut Class grader to match the AGS000 princess cut grade, but have said that once you have an AGS000 princess, your worries about cut quality issues are over, so you don't need to screen further.

The AGA tool is a way to screen non[/b-] AGS000 princess cuts, those which do not seek to meet the AGS cut style that has become their well respected Brand of princess cut diamond. There are hundreds of times more regular cut princess stones than those AGS has graded, many of which are worthy of consideration, especially by those people who are not the total perfectionist, those who are not necessarily into a "brand", or those who want to shop far more broadly for a "best" overall deal rather then totally go for the premium branded products.

You would be extremely hard pressed to find a 1A , 1B or 2A princess cut but they do exist and I think they likely have merit in cut and appearance, but it is a screening situation and you need to look and decide if it works on a particular diamond.

Thanks for the explanation. It makes a lot of sense. I had actually found a diamond that was graded 1A, but that turned out to have a small chip on it as I had posted in another thread. This new diamond (graded 3A based on the girdle thickness) actually looks like it has better light performance than the original 1A diamond just by comparing the ASET images. This new diamond also meets all of my basic parameters in terms of the 4C's. The only downside seems to be the thickness of the girdle, so I'm trying to evaluate how important the girdle thickness is and whether that alone should dissuade me from purchasing the diamond. I understand that the thick girdle means that more of the weight is concentrated along the girdle, which means for a "smaller" looking stone. Are there any other considerations that I may be missing?

 

[JulieN]

I think it looks good. Is there a video of it? Price/budget?

 

[tenniz23]

I think it looks good. Is there a video of it?

Here's the 360 view on JA: http://www.jamesallen.com/loose-diamonds/princess-cut/1.71-carat-i-color-vs1-clarity-sku-222341

 

[JulieN]

Budget for diamond?

 

[tenniz23]

Budget for diamond?

My budget is around $10k-11k.

 

[GoSounders]

What's the price of this diamond?

If the price reflects the smaller spread due to the girdle, there should be no issue with a thick-very thick girdle and it's a good buy. However, if the price is similar to other well-cut 1.7ct stones with larger spreads (and smaller tables), I'd say this isn't the stone for you.

 

[JulieN]

I don't know if this one would fit the ring that has already been designed better than your new choice. http://www.jamesallen.com/loose-diamonds/princess-cut/1.87-carat-i-color-vs2-clarity-sku-232185

 

[tenniz23]

What's the price of this diamond?

If the price reflects the smaller spread due to the girdle, there should be no issue with a thick-very thick girdle and it's a good buy. However, if the price is similar to other well-cut 1.7ct stones with larger spreads, I'd say this isn't the stone for you.

The price for this diamond is $9700.

There is also a 2nd diamond that I"m considering at the moment. It's the same carat size, but an H color (instead of I) and VS2 (instead of VS1). It's $1600 more expensive and its ASET doesn't quite look as good. Here's a comparison of the 3A's ASET (on the left) and the 1A's ASET (on the right):



The 1A diamond does have a larger spread.

 

[tenniz23]

I don't know if this one would fit the ring that has already been designed better than your new choice. http://www.jamesallen.com/loose-diamonds/princess-cut/1.87-carat-i-color-vs2-clarity-sku-232185

I did actually consider that one for a while, but I had ruled it out due to an inclusion visible in the 360 degree video. It's slightly to the right of the center of the table and looks like an upside-down V. That was pretty much the only reason I excluded it, because I thought that it might not be eye-clean. I understand it's a magnified image, but I don't really have a good sense of what it'll look like in real life. I can always reconsider though...

 

[JulieN]

I saw it, too. I am already straining to see it on my screen, I think it will be eye-clean, it is somewhat transparent. Video of the H? Or which one did JA recommend?

 

[tenniz23]

I saw it, too. I am already straining to see it on my screen, I think it will be eye-clean, it is somewhat transparent. Video of the H? Or which one did JA recommend?

Here is the H: http://www.jamesallen.com/loose-diamonds/princess-cut/1.71-carat-h-color-vs2-clarity-sku-215803
Between the two, JA recommended the I (graded 3A), but now you've got me thinking about the 1.87ct! There's no emoticon for it, but :twitch:

 

[JulieN]

I think this is the closest we have:

Those triangular leakage areas on the side like the H has tends to get worse with some tilt.

 

[tenniz23]

I think this is the closest we have:

Those triangular leakage areas on the side like the H has tends to get worse with some tilt.

Yeah, I think the 1.87ct also has that leakage on the sides by looking at the 360 degree image.

So does the 3A diamond look like a good value for the price?

 

[diamondseeker2006]

I don't know if this one would fit the ring that has already been designed better than your new choice. http://www.jamesallen.com/loose-diamonds/princess-cut/1.87-carat-i-color-vs2-clarity-sku-232185

This stone is a much better size than the first one you linked at 6.7x6.9mm. There is no point in buying a stone that has the weight of 1.7 but looks like a smaller stone.

 

[tenniz23]

I don't know if this one would fit the ring that has already been designed better than your new choice. http://www.jamesallen.com/loose-diamonds/princess-cut/1.87-carat-i-color-vs2-clarity-sku-232185

This stone is a much better size than the first one you linked at 6.7x6.9mm. There is no point in buying a stone that has the weight of 1.7 but looks like a smaller stone.

What is a good size (in mm) for a 1.7ct princess cut? Judging from several diamond size charts that I found online, it should be about 6.9-7.0mm, which I honestly have not seen at all. According to these charts, it seems that the 3A diamond I found is smaller than what a 1.5ct should be. In fact, even the 1.87ct diamond is small for its weight. The charts peg its size somewhere between 1.6-1.7ct.