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GIA Excellent cut does not grade well in HCA ***help needed!

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Re: GIA Excellent cut does not grade well in HCA ***help nee

Again being a newbie to diamonds, all this info is overwhelming.

If I had not stumbled on to the HCA tool, I would have already purchased that diamond and perhaps been very satisfied. It looked great(again my eyes are not trained for this), and I would have the GIA cert which from what I've been told, is pretty much the best assurance you can have.

Coming into this, I was told if GIA or AGS rate a cut as excellent, I would have nothing to worry about. Yes some GIA excellent are better than others, but wasn't this category listed by GIA to weed out the duds and focus on what the stone looks like to the eye? Shouldn't there be only a certain percentage of variance?

From an article I read on another website, some poor HCA scores which do not grade favorably look better to the eye than those with scores in the 1-2 range.

So from what I understand, GIA scores are calculated not only on equations and angles/percentages, but how the stone looks/performs to the eye. If this is true then wouldn't the HCA be more useful in the case of a non certified stone, or one with certification from EGL or another less-regarded lab?

I think I have enough info to make an educated decision at this point... who knows!!?
 
Re: GIA Excellent cut does not grade well in HCA ***help nee

I agree Rock- in this context, it's totally overwhelming for a newbie- in fact, it's even that way for an "old-bee"
I'm still kind of amazed that people make such definitive statements about a stone they've never seen firsthand- declaring them problematic based on GIA's angle measurements alone
GIA's EX cut grade does have some variation- but the "tempest in a teacup" analization of stones given GIA's grade does not go on in the "real world" market.
That is to say- the HCA has no negative bearing whatsoever on a GIA EX cut graded diamond's price.
For those who can see the difference and want a stone which scores well on HCA, it might involve a premium in the price- and for some people, it's well worth it.

But it seems you're taking a very sensible, well thought out approach
 
Re: GIA Excellent cut does not grade well in HCA ***help nee

rockshopping555|1332250749|3152723 said:
So from what I understand, GIA scores are calculated not only on equations and angles/percentages, but how the stone looks/performs to the eye.
Mostly by members of the trade, not consumers and in an artificial lighting environment that has some issues.
People who sell steep deep diamonds every day are going to say they like them.
It was not an unbiased double blind study that would be acceptable as real science in other areas of study.
Such a study has never been done that I have heard of or seen the results of.
The biggest problem would be in order to do it right the people doing the reviews would have to live with the diamonds in their own environments and life for at least a couple days to get valid results.
 
Re: GIA Excellent cut does not grade well in HCA ***help nee

One thing I will say... there have been AGS0 stones that have scored in the 5's on the HCA. It's a limited tool. And that's why we say: Get an Idealscope. We also say: AGS0 trumps HCA.

Ultimately the most thorough approach is a combination of: education on diamond angles so you understand what combination will give you what type of light return, experience so you know what type of light return appeals to you (because this is personal), reliable labs report to inform you about individual stones, HCA to reject, an Idealscope to chose and and your own eyes to confirm that you like the appearance and performance of the stone.

But not everyone sees the need to be that thorough. For some, any AGS0 is good enough. For others any GIA Ex/Ex is good enough. For yet a different group: no lab report is fine.

The point is to find out what approach to finding a stone is right for you.
 
Re: GIA Excellent cut does not grade well in HCA ***help nee

So from what I understand, GIA scores are calculated not only on equations and angles/percentages, but how the stone looks/performs to the eye. If this is true then wouldn't the HCA be more useful in the case of a non certified stone, or one with certification from EGL or another less-regarded lab?
HCA is a tool made by 1 person using his opinion of what looks good. His opinion while useful is still his own opinion.

GIA and AGS have different sets of opinions. That's why there's variance between GIA AGS and HCA in terms of what's an excellent/ideal stone. What Holloway thinks looks good may not be what looks good to another person. My personal preference has been somewhat inline with HCA but I have liked many stones between 2-4 and have disliked many stones <1. Once again, it's a tool that is helpful but it is definitely not definitive. A certain score does not mean buy buy buy and another score means run run run.
 
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