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Help! GIA Excellent Cut Vs. HCA

It sure has been a long road, quite exhausting actually. I just think it is a real shame that people can weed out an AGS0 and GIA Ex,Ex,Ex stone that can score top on the brilliance scope because it gets above 2 on an HCA score. it is well known that HCA favors shallow cuts, and as you say some unattractive stones get through and some beautiful top performers get passed on.

I like how yssie said there is no point quibbling over 0.2 degrees etc, and that no one believes it's a fool proof method anyway. Paralysis by analysis can happen - as this site has shown. When you think about the percentages of stones that are above 1 carat, then the percentages that are GIA ex ex ex and then the percentages that are AGS0...we are really overanalysing things!!!

HCA is meant to predict light performance, and Gary H does like shallower stones, and Gemologists have questioned that as top performing stones classed GIA triple ex and AGS0 can get weeded out, those that score top on the brilliance scope, and yet non ideal and non ex stones can pass.

Such a long thread! :shock:
 
2023|1342227603|3233564 said:
It sure has been a long road, quite exhausting actually. I just think it is a real shame that people can weed out an AGS0 and GIA Ex,Ex,Ex stone that can score top on the brilliance scope because it gets above 2 on an HCA score. it is well known that HCA favors shallow cuts, and as you say some unattractive stones get through and some beautiful top performers get passed on.

I like how yssie said there is no point quibbling over 0.2 degrees etc, and that no one believes it's a fool proof method anyway. Paralysis by analysis can happen - as this site has shown. When you think about the percentages of stones that are above 1 carat, then the percentages that are GIA ex ex ex and then the percentages that are AGS0...we are really overanalysing things!!!

HCA is meant to predict light performance, and Gary H does like shallower stones, and Gemologists have questioned that as top performing stones classed GIA triple ex and AGS0 can get weeded out, those that score top on the brilliance scope, and yet non ideal and non ex stones can pass.

Such a long thread! :shock:
Click to expand...

Just an interesting fact....Garry also invented the idealscope. He has been an incredible contributor to the diamond industry and this forum. A true expert in his field. :appl:
 
2023|1342227603|3233564 said:
It sure has been a long road, quite exhausting actually. I just think it is a real shame that people can weed out an AGS0 and GIA Ex,Ex,Ex stone that can score top on the brilliance scope because it gets above 2 on an HCA score. it is well known that HCA favors shallow cuts, and as you say some unattractive stones get through and some beautiful top performers get passed on.

I like how yssie said there is no point quibbling over 0.2 degrees etc, and that no one believes it's a fool proof method anyway. Paralysis by analysis can happen - as this site has shown. When you think about the percentages of stones that are above 1 carat, then the percentages that are GIA ex ex ex and then the percentages that are AGS0...we are really overanalysing things!!!

HCA is meant to predict light performance, and Gary H does like shallower stones, and Gemologists have questioned that as top performing stones classed GIA triple ex and AGS0 can get weeded out, those that score top on the brilliance scope, and yet non ideal and non ex stones can pass.

Such a long thread! :shock:
Click to expand...


did you get my post on your other forum?

[URL='https://www.pricescope.com/community/threads/help.177415/page-3']https://www.pricescope.com/community/threads/help.177415/page-3[/URL]
 
Angietime, agpoula was the original poster on that last thread. I was just trying to explain in that thread that an OEC was different to a Modern Round Brilliant. Last I read Gypsy was setting agpoula up with vendors - if he is still looking no doubt he will reply to you! Fyi this thread is actually fifes thread who is after info too on the diamond posted in the first post.
 
Just for the record, my original stone was a picture perfect H&A that had all the perfect AGS Ideal/GIA EX numbers. The stone I bought next after a lot of time and education on here (mainly due to Yssie), I bought a GIA XXX that had an HCA score over 2. But in order to do that step, I had Jonathan at GOG call in the stone for me and make sure it was a brilliant stone and that it didn't have too much leakage. The stone does have a tiny spot of leakage, but in actuality, there is no negative effect and you certainly can't see it. It holds it's own next to my other perfectly cut diamond. So I am hearing what you are saying, 2023, it is just that when people are trying to get a great stone, it is safer to steer them within tighter parameters, especially when they aren't going to have someone analyze the stone for light performance like I did. And just for the record, people should not be using the HCA on AGS Ideal cut stones! If I see that, I ALWAYS tell them not to do that since AGS has already evaluated the stone as having ideal light performance!
 
Angietime, I'm not the original poster in this thread either :lol: I was just pointing out how the HCA can cut off beautifully cut stones that fall in the spot for AGS0 and GIA ex cuts, yet also let not well cut stones pass that would fail on AGS/GIA and AGA as ideal cut stones.

DiamondSeeker, yes, I've also read that a Hearts and Arrow diamond did not pass HCA and yet as you say is a beautiful stone and can be considered the top tier of diamond cutting.

:))
 
Thanks everyone for the feedback. I've been reading all of your posts, but still am not really qualified to reply to any of them.

I've decided to go ahead with ordering the diamond. To me, not an expert, the photos all look really good. After all the good things I've heard about GIA over the months, I'm not going to reject this diamond based on some online tool that I only just heard about, until I actually see it. Plus, excel is offering me a 100% refund if I'm not satisfied.

I'll post photos for you all in a week or two when it arrives. I'll try to get a video of it as well.

Thanks again!

-Fife
 
Hi Fife!

That second one DiamondSeeker posted looks great? Its an AGS Ideal, and its proportions look good! Its another example of an AGS0 which would fail HCA by 0.2 on the pav angle (so just a smidge of a fail). The stone you currently have I don't think would be considered and AGS ideal, more a VG. I think this stone DS posted is def worth a look at, at that price!

The first link, the cert didn't come up accurately, it was an I colour stone in the cert (prob a glitch)

The second one will save you 1500 extra or so...
 
Just another thought, VS1 is quite a high clarity, you could go to VS2 and G colour, a nice combination.
 
Oh, thanks for catching that, 2023! Something definitely wrong with that first cert! The other one works with the angles because the crown angle is complimentary to the pav. angle.
 
No worries! Just saying it still gets a 2.5 even though its an AGS0 :)

I'm glad we found him again! I thought we had completely lost him :))
 
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