Holloway Cut Adviser

[dolby77]

I was practicing using the cut adviser on this site using the GIA reports from bluenile.com. All the "signature ideal" cut and "ideal" cut diamonds came back with this error "The total depth % you entered suggests the girdle is dangerously thin, or the data you entered is incorrect." Which I don''t really understand...

Also, diamonds they have as "Excellent" with "very good" symmetry come back as "fish eye - do not purchase".

Am I totally missing something or what?!?!

 

[neatfreak]

Many GIA Ex stones aren''t really that great. Do you have an example of a stone you ran through and it didn''t come out right? It''s also possible that there''s user error.

 

[Moh 10]

Are you sure you are not entering percentages when it expects angles?

 

[dolby77]

http://www.bluenile.com/pop_int_cert_view.jsp?pid=LD01389738 is the link to the GIA report from the bluenile.com site.

And if excellent cuts aren''t that great, what should I be looking for? The more I look for a diamond the more I feel it''s impossible to understand all the aspects of looking for one.

Also, when buying a diamond from one of price scope vendors, can you even see the crown and pavilion %?? for most i can ''t find the GIA report...


thanks

 

[dolby77]

from the looks of it you can''t even enter the depth in angles...only percentages...

 

[neatfreak]

Date: 11/24/2008 9:19:32 PM
Author: dolby77
http://www.bluenile.com/pop_int_cert_view.jsp?pid=LD01389738 is the link to the GIA report from the bluenile.com site.


And if excellent cuts aren''t that great, what should I be looking for? The more I look for a diamond the more I feel it''s impossible to understand all the aspects of looking for one.


Also, when buying a diamond from one of price scope vendors, can you even see the crown and pavilion %?? for most i can ''t find the GIA report...



thanks

So I think there is a bit of user error here, because when I insert those numbers from that GIA report I get a score of 0.9.

And you are doing just the right thing with GIA Ex cuts by plugging them into the HCA. THAT can tell you whether it really is likely to be a nice stone or not.

But I''m not sure what you are doing wrong here...

Most of the PS vendors provide the certificates for in house diamonds. What vendors are you looking at that don''t?

 

[beach]

The cut advisor sometimes has these errors. I have experienced them as well. Some days input data and I get the same info, some days I input the same data and it gives a score.

 

[swingirl]

Never had any errors using the HCA unless something was entered incorrectly. This stone comes in at a .9. Anything 2 or below is worth further consideration.

Just make sure you know the difference between crown/pavilion angle and crown/pavilion percent.

 

[Kelli]

I did have a GIA excellent that scored poorly on the HCA. It really wasn''t pretty though and now that it''s recut and beautiful it scores under 2.

 

[Lisa Loves Shiny]

Date: 11/24/2008 10:02:29 PM
Author: beach
The cut advisor sometimes has these errors. I have experienced them as well. Some days input data and I get the same info, some days I input the same data and it gives a score.

Me too.

 

[Kelli]

Make sure you get the crown and pavilion angles. If they send you a copy of the report, you should be able to see them. The GIA allows way too many diamonds into their excellent cut grade. They''re not all so good, I experienced that first hand. AGS0 is a more reliable cut grade, but if you''re looking at GIA stones you just have to make sure they score well on the HCA and have good idealscope images.

 

[Garry H (Cut Nut)]

You are mixing angles with %''s

 

[dolby77]

For instance, I though Solomon Brothers and James Allen are a few that I found to have incomplete GIA reports...meaning I didn''t see the crown or pavilion % numbers...

Ok, new question. So is it better for me to put less weight on the cut and more weight on the holloway cut adviser??? Meaning that sometimes a very good cut can have better HCA characteristics making it a diamond that will return more "light", "fire" and "scintillation" than an excellent cut diamond?

I''m turning into a diamond junkie and I only want to buy one!!!! ahhhh!

Thanks!!

 

[Lorelei]

Date: 11/25/2008 4:16:42 PM
Author: dolby77
For instance, I though Solomon Brothers and James Allen are a few that I found to have incomplete GIA reports...meaning I didn't see the crown or pavilion % numbers...

Ok, new question. So is it better for me to put less weight on the cut and more weight on the holloway cut adviser??? Meaning that sometimes a very good cut can have better HCA characteristics making it a diamond that will return more 'light', 'fire' and 'scintillation' than an excellent cut diamond?

I'm turning into a diamond junkie and I only want to buy one!!!! ahhhh!

Thanks!!

The HCA is used for eliminating lesser performers, not for selecting diamonds. The cut of a diamond is all important in order for you to have a beautiful stone, so ideally you want to evaluate each diamond as a whole, looking at its depth, table, crown and pavilion angles, girdle thickness, polish and symmetry and diameter measurements at a minimum. The HCA can only estimate the performance of any given diamond, it can't physically see the diamond and in addition there are various factors it can't predict. So you use the HCA to basically see which diamonds score 2 or below. Once you have contenders which do, you then evaluate using * Idealscope images and trusted vendor/ appraiser input and your own eyes when deciding to purchase or make a purchase final. Also grading reports without all the info are likely to be pre cut grade from GIA.

Also with terms such as Very Good cut, Excellent cut etc, even if used as a GIA cut grade, you need to carefully evaluate each diamond as the criteria for these cut grades is broad. AGS 0 is usually considered to be the premier cut grade, but with GIA there can be more variance which can allow for some less desirable cut combinations. Also these labels used by vendors to describe their ' Ideal Cuts', Premium Cuts etc does not guarantee you a well cut diamond so again evaluate each diamond on its own physical proportions and desirable visual properties ( * as above).

 

[dolby77]

so that means that an excellent diamond may under perform a very good diamond on the HCA scale right? meaning to eliminate that particular diamond?

 

[Stone-cold11]

Date: 11/25/2008 4:16:42 PM
Author: dolby77
For instance, I though Solomon Brothers and James Allen are a few that I found to have incomplete GIA reports...meaning I didn''t see the crown or pavilion % numbers...

Ok, new question. So is it better for me to put less weight on the cut and more weight on the holloway cut adviser??? Meaning that sometimes a very good cut can have better HCA characteristics making it a diamond that will return more ''light'', ''fire'' and ''scintillation'' than an excellent cut diamond?

I''m turning into a diamond junkie and I only want to buy one!!!! ahhhh!

Thanks!!

Those are probably older GIA reports, if the stones are from after jun 2006, I think, you should be able to get the angles off from the GIA reportcheck website.

That is what I do, I disregard the cut grading of GIA reports too but that means you will be going through alot more stones to find a good one but that it could get you a better deal as you are not paying the premium for a GIA ideal cut, assuming you understand what the graph on the HCA represents and what you are getting into.

 

[Lorelei]

Date: 11/25/2008 4:24:29 PM
Author: dolby77
so that means that an excellent diamond may under perform a very good diamond on the HCA scale right? meaning to eliminate that particular diamond?

Yes. But do remember that the cut advisor is used for elimination and not selection. Also some diamonds with a steeper pavilion angle for example may not score so well on the cut advisor but actually be nice diamonds in some cases, so do go by aids which can actually represent the diamond such as Idealscope and the advice of the trusted vendor you are working with when seriously considering a diamond for purchase.

 

[dolby77]

could you double check my understanding...which I''m not sure I do. I just plugged in this diamond...

depth 60.5
table 59
crown 34.4
pavilion 40.6

it comes back with a 1.1 and the "X" on the graph falls within both the green and white outlines meaning it''s a candidate for excellent and ideal cut, right?

however, its only given a "very good" cut, good polish and good symmetry. So why the difference?

 

[Lorelei]

Date: 11/25/2008 4:40:42 PM
Author: dolby77
could you double check my understanding...which I'm not sure I do. I just plugged in this diamond...

depth 60.5
table 59
crown 34.4
pavilion 40.6

it comes back with a 1.1 and the 'X' on the graph falls within both the green and white outlines meaning it's a candidate for excellent and ideal cut, right?

however, its only given a 'very good' cut, good polish and good symmetry. So why the difference?

GIA cut grade is broad and there can be various factors which can affect a diamond not getting an Excellent cut grade, girdle thickness, faceting, brillianteering amongst some reasons. But some of these diamonds can still be well cut stones and be well worth considering. There are really no hard and fast rules as there can be various reasons which can cause a diamond to be within one cut grade whereas you would think it would qualify for another, so that is why it pays to evaluate each diamond on its own merits and proportions and not rely too much on these cut grades, unless it is an AGS0 which is normally a reasonable bet that you will get a well cut diamond.

 

[swingirl]

I am only guessing at this... The HCA is going only by the numbers you plug in but has no way of knowing how the symmetry has been cut (or if the stone has any other issues that knock it out of the excellent range). If this stone has ideal angles but is only "good" in symmetry than it will NOT get an ideal or excellent grade.

In other words there are other things GIA and AGS consider in giving their grades, not just the numbers.

 

[dolby77]

Ok, in summary let me see if I can get this right...

The HCA is good for seeing how good the cut angles and percentages are, and thus helps to eliminate diamond cuts that are not within an decent range. thus an excellent diamond may fall short of expectations in the HCA in some cases.

HOWEVER, other factors like excellent symmetry and polish (though not color or clarity, right?) may make up for the shortcomings and therefore make it an excellent stone.

yes? no?

 

[Lorelei]

Date: 11/25/2008 8:48:04 PM
Author: dolby77
Ok, in summary let me see if I can get this right...

The HCA is good for seeing how good the cut angles and percentages are, and thus helps to eliminate diamond cuts that are not within an decent range. thus an excellent diamond may fall short of expectations in the HCA in some cases. Yes.

HOWEVER, other factors like excellent symmetry and polish (though not color or clarity, right?) may make up for the shortcomings and therefore make it an excellent stone. Not necessarily. The angles are the crucial factors which drive light return or sparkle, if the angles aren't in a good range polish and symmetry won't save it. However if you get some diamonds which fall into a grey area on the HCA, say between 2 and 3, if they have top symmetry in some cases these can be worth consideration if you can get Idealscope images or have trusted vendor recommendation.

yes? no?

So in conclusion, use the HCA to see which diamonds score 2 or below. Once you have these, find the ones which best suit your budget, colour, clarity and carat requirements. Request Idealscope images for these where possible.