GIA Excellent but not great on HCA? help!

[Bailey707]

I'm looking to purchase a GIA graded excellent RB...but when I entered in the info into HCA it scored a 3.7, how could it be graded excellent but not perform well?

Stats:

1.21 carat SI2
J color

Depth: 62.6
Table: 57
Crown Angle: 35
Crown Height: 15
Pavilion Angle: 41.2
Pavilion Depth: 43.5

Polish: Very Good
Symmetry: Excellent
Strong Blue Fluor

 

[stone-cold11]

If you look at the color plot of the HCA, it shows the proportions range given by GIA for their Ex grade, compared to AGS Ideal and HCA.

More reading for you.
https://www.pricescope.com/journal/laboratory_cut_grades_what_report_doesn’t_show

 

[Bailey707]

I'm sorry, I've very new to all of this so I am still a bit confused. Do you believe then, that its HCA score should deter me from this specific diamond?

 

[Garry H (Cut Nut)]

It can look very nice set in a high 4 prong setting.
But if you do not keep it clean you will see some dead zones just inside the table.

 

[denverappraiser]

I'm sorry, I've very new to all of this so I am still a bit confused. Do you believe then, that its HCA score should deter me from this specific diamond?

No

 

[Dreamer_D]

There are a few different pieces of information that you can use to help you choose a diamond. Each piece of information will help you to narrow the possible choices down to the best cuts.

One is cut grade. Another is the HCA. Another is an ideal-scope image. Another is your eyes.

You can emphasize any or all of these in your selection.

For most people, GIA Ex cut grade is enough for them, it means it is a well cut stone. The HCA score is suggesting this is not the *best of the best* from among GIA Ex cuts -- GIA has a wider target for GIA Ex than many cut nuts prefer. If that matters, then consider looking further for a stone that is both GIA Ex and has an HCA score under 2. If that does not matter to you, then consider the stone further, perhaps by seeing it in person and comparing it to other diamonds that do score well on the HCA or that have an AGS0 cut grade, a stricter lab for cut.

 

[Rockdiamond]

I'm sorry, I've very new to all of this so I am still a bit confused. Do you believe then, that its HCA score should deter me from this specific diamond?

No

+1
I don't care how well cut any diamond is, if it gets dirty, it will not look the same as it did clean.
I'd also take issue with the statement that a stone has to score well on HCA to be "the best of the best" in terms of cut.

I have experienced many cases where I will prefer the cut of a stone scoring poorly on the HCA versus one that scored higher- both GIA Triple EX.

 

[Amys Bling]

I'm sorry, I've very new to all of this so I am still a bit confused. Do you believe then, that its HCA score should deter me from this specific diamond?

No

+1
I don't care how well cut any diamond is, if it gets dirty, it will not look the same as it did clean.
I'd also take issue with the statement that a stone has to score well on HCA to be "the best of the best" in terms of cut.

I have experienced many cases where I will prefer the cut of a stone scoring poorly on the HCA versus one that scored higher- both GIA Triple EX.

I think this is why you should also heavily rely on your eyes as a tool. To each his own and when you see a stone that speaks to you that can/may trump all other tools and grading.

 

[Garry H (Cut Nut)]

I'm sorry, I've very new to all of this so I am still a bit confused. Do you believe then, that its HCA score should deter me from this specific diamond?

No

+1
I don't care how well cut any diamond is, if it gets dirty, it will not look the same as it did clean.

Go test it David. Report back.

 

[Rockdiamond]

Garry, after having made as many rings as we have ( many thousands) and also serviced them, I would say the setting, and other factors such as the type of dirt involved may have the most impact on dirt, diamonds, and how they interact.

So I'd ask you- take a diamond scoring 0 on the HCA, and rub some hand cream on it.
If it still looks just as shiny as it did when it was clean, I'll kiss your butt in Macy's window

IT'S A JOKE!! ( the part about Macy's anyway)

 

[Garry H (Cut Nut)]

Garry, after having made as many rings as we have ( many thousands) and also serviced them, I would say the setting, and other factors such as the type of dirt involved may have the most impact on dirt, diamonds, and how they interact.

So I'd ask you- take a diamond scoring 0 on the HCA, and rub some hand cream on it.
If it still looks just as shiny as it did when it was clean, I'll kiss your butt in Macy's window

IT'S A JOKE!! ( the part about Macy's anyway)

I have done the tests but you have not.

If somone has the time please find the thread where Drena wore a shallow and tolkowsky pair of earrings to Vegas 4-5 years ago.

You could discuss it with 20 posts and waste hours of many peoples time, or David, simply do some real comparison tests.

 

[Rockdiamond]

Garry, I'm not trying to be flippant. My point is that my experience in the trade has presented me with many diamonds that have been worn. So even without performing whatever test you'll suggest, I have seen the results of dirt, and diamonds. I've seen these results on a myriad of diamond cuts.
My points:
1) the type of setting design has a huge impact on how much dirt a diamond picks up- then the setting impacts how it looks once dirty.
2) the type of dirt has a huge impact. A dusty ring is rather easy to clean. But some ladies have a habit of applying hand cream while wearing their diamond. If that's the case, cleaning becomes much more difficult- furthermore, no matter how well cut a diamond is ( or it's HCA score) if it's had hand cream applied to it, it's not going to sparkle.

To save time, please tell us what specifically your test is, in terms of procedure.
Since you've probably done whatever test you're going to suggest, what were the results you obtained?

 

[Garry H (Cut Nut)]

the test you described earlier is a great start

do any test that you can think of to replicate what you have seen

 

[Rockdiamond]

This is so easy Garry.
No need to waste anyone's time- no one is being forced to read this.
My position is that HCA score, and how a diamond looks when dirty, are unrelated.

If we are comparing , for example, a RBC, and a Marquise, then I do believe that we can show a difference on how a diamond gathers dirt- and the effect of that on it's appearance. This based on drastically differing pavilion facet size and angle.
However between two RBC's- both GIA EX cut grade, yet having drastically widely varying HCA scores, I do not believe you can show any difference in how they will visibly react to dirt.

 

[Garry H (Cut Nut)]

This is so easy Garry.
No need to waste anyone's time- no one is being forced to read this.
My position is that HCA score, and how a diamond looks when dirty, are unrelated.

If we are comparing , for example, a RBC, and a Marquise, then I do believe that we can show a difference on how a diamond gathers dirt- and the effect of that on it's appearance. This based on drastically differing pavilion facet size and angle.
However between two RBC's- both GIA EX cut grade, yet having drastically widely varying HCA scores, I do not believe you can show any difference in how they will visibly react to dirt.

So in your turest form you will not even try?

 

[Rockdiamond]

Hi Garry- let me first say I'm kind of jealous looking at all the fun photos from Las Vegas- As you surely know, I could not make it- and one of my big regrets about not being able to be there was that I missed meeting you face to face.

I do very much respect your research- regardless of whether or not I agree. Meeting you would be an honor- and great fun.
In this case, I am asking you to share the results of your test- and also the methodology.
If you want to give me an idea how you tested stones to back up the claim ( I think) you're making ( that being: A diamond that scores better ((lower)) on HCA will show less effect from dirt) I would be interested in the results, and how you obtained them.

 

[Garry H (Cut Nut)]

Hi Garry- let me first say I'm kind of jealous looking at all the fun photos from Las Vegas- As you surely know, I could not make it- and one of my big regrets about not being able to be there was that I missed meeting you face to face.

I do very much respect your research- regardless of whether or not I agree. Meeting you would be an honor- and great fun.
In this case, I am asking you to share the results of your test- and also the methodology.
If you want to give me an idea how you tested stones to back up the claim ( I think) you're making ( that being: A diamond that scores better ((lower)) on HCA will show less effect from dirt) I would be interested in the results, and how you obtained them.

do one yourself because you will never believe anyone else.
And search for the test I mentioned above

 

[Rockdiamond]

I think this discussion highlights some very important distinctions between the way each of us looks at diamonds.
Garry, you have devised some very sophisticated methods to judge the way a diamond is cut.

Personally, I feel that judging diamonds is best done by eye, using the most basic of tools.
Loupe, tweezer, Millimeter gauge, diamond lamp, and other various lighting scenarios.

So, I would not even begin to know how to devise the test you suggest.
Furthermore, another rift between our positions is that I have used the tools you invented, and not agreed with the results they have provided.
But I have noticed that there have been many cases here on PS where people have found the tools you invented to be very useful.
I would not like to be on record as saying the tools you invented are "wrong"- just that either method has it's pluses and minuses.


Having said that, I am asking about this statement, written by you

I'm sorry, I've very new to all of this so I am still a bit confused. Do you believe then, that its HCA score should deter me from this specific diamond?

No

+1
I don't care how well cut any diamond is, if it gets dirty, it will not look the same as it did clean.

Go test it David. Report back.

Can you clarify what your point is?

 

[Garry H (Cut Nut)]

You are doing it again David.

It is simple
waste not your words and spend 10 minutes making some diamonds dirty and see for your self.

I will no longer respond to your words until you do something.

Look up http://www.youtube.com/watch?v=uoBXAUNU1HE and spend all 3.35 minutes (ignore the racism) and see if you can get my point (and have a laugh at the same time).

 

[Dancing Fire]

Hi Garry- let me first say I'm kind of jealous looking at all the fun photos from Las Vegas- As you surely know, I could not make it- and one of my big regrets about not being able to be there was that I missed meeting you face to face.

I do very much respect your research- regardless of whether or not I agree. Meeting you would be an honor- and great fun.
In this case, I am asking you to share the results of your test- and also the methodology.
If you want to give me an idea how you tested stones to back up the claim ( I think) you're making ( that being: A diamond that scores better ((lower)) on HCA will show less effect from dirt) I would be interested in the results, and how you obtained them.

i'll pay $2000 bucks for a ring side seat...

 

[Rockdiamond]

No problem Garry- you actually have responded, in your lack of response. Furthermore, if you have some sort of proof that the HCA can tell us which diamond looks best when dirty, this would be a great place to produce it.

To the op- this discussion should ease your mind.
The HCA has it's defenders- including many trusted members of Pricescope. Many have used it, and with great results.
Yet, outside of Pricescope it's not a widely accepted method of judging how well a diamond is cut.
The GIA "EX", or AGSL "0" cut grade are widely accepted methods of assessing cut quality.

Trust your eyes.
Verify with a GIA or AGSL report.

 

[Garry H (Cut Nut)]

you prove it and trust your eyes