GIA Excellent = HCA 6!

[phoenixgirl]

I was designing myself imaginary rings and found this diamond:

1.44 GIA excellent that scores a 6.0 on the HCA. Yikes, I pity the poor person who buys this thinking it''s a well cut stone!

 

[honey22]

Wow, I checked that cos I couldn't really believe it (sorry!). That's incredible. With those measurements, it doesn't even look round!
Maybe Gary or another expert can chime in and explain this. How on earth can this stone get an excellent cut grade? It is an error in the grading report?

Just goes to show how lucky we are to have tools such as the HCA and IS! And PS!!!!

 

[Deelight]

But if I am not mistaken if you look at the HCA it still falls within the boundaries for a GIA excellent

 

[elle_chris]

Doesn''t GIA grade cut based on human observation. Apparently someone at GIA thought it looked "excellent".
Maybe that crown angle and pavilion work well with eachother even though they''re both waay outside of the ideal range.

Not a stone I''d pick or recommend but who knows...

 

[ImpatientOne]

Hmm, the listing also says it is an "Ideal" cut stone!

 

[elle_chris]

I''m really wondering what this stone looks like!!!
Would this be like a bright stone without much fire? (the crown and pavilion angles still confuse me)

 

[strmrdr]

small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

 

[Garry H (Cut Nut)]

Date: 3/8/2008 7:30:16 PM
Author: elle_chris
Doesn''t GIA grade cut based on human observation. Apparently someone at GIA thought it looked ''excellent''.
Maybe that crown angle and pavilion work well with eachother even though they''re both waay outside of the ideal range.

Not a stone I''d pick or recommend but who knows...

GIA does not look at diamonds with the naked eye for cut quality (other than for polish, sym and girdle thickness, all under magnification).

They did a study where a number (?100- 500? cant remember) looked at some stones in controled light which makes many fancy cuts look better than rounds. Then they applied those proportions to a very similar system to HCA (which I have a patent for).
GIA and a group of my associates have had words over the flaws in their approach as reported here
http://journal.pricescope.com/Articles/50/1/Letter-to-the-Editor-of-the-Australian-Gemmologist.aspx

 

[Garry H (Cut Nut)]

Date: 3/8/2008 8:41:16 PM
Author: strmrdr
small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

I think you would see it easily Storm

 

[strmrdr]

Date: 3/9/2008 3:25:54 AM
Author: Garry H (Cut Nut)

Date: 3/8/2008 8:41:16 PM
Author: strmrdr
small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

I think you would see it easily Storm

in a bezel yea in a high 4 prong it would be harder too see.

 

[Garry H (Cut Nut)]

true
but it will still look bad when it is dirty

 

[strmrdr]

Date: 3/9/2008 4:18:00 AM
Author: Garry H (Cut Nut)
true
but it will still look bad when it is dirty

yea....

 

[diagem]

Date: 3/9/2008 3:47:41 AM
Author: strmrdr

Date: 3/9/2008 3:25:54 AM
Author: Garry H (Cut Nut)

Date: 3/8/2008 8:41:16 PM
Author: strmrdr
small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

I think you would see it easily Storm

in a bezel yea in a high 4 prong it would be harder too see.

Question..., how would this C & P combination look "virtually" if the lgf''s would be painted and shortened and to 70%?

 

[Garry H (Cut Nut)]

Date: 3/9/2008 4:23:06 AM
Author: DiaGem

Date: 3/9/2008 3:47:41 AM
Author: strmrdr

Date: 3/9/2008 3:25:54 AM
Author: Garry H (Cut Nut)

Date: 3/8/2008 8:41:16 PM
Author: strmrdr
small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

I think you would see it easily Storm

in a bezel yea in a high 4 prong it would be harder too see.

Question..., how would this C & P combination look ''virtually'' if the lgf''s would be painted and shortened and to 70%?

you can improve it, but not save its life DG
And by improving it GIA would bing you for "brillianteering"

 

[diagem]

Date: 3/9/2008 4:29:31 AM
Author: Garry H (Cut Nut)

Date: 3/9/2008 4:23:06 AM
Author: DiaGem

Date: 3/9/2008 3:47:41 AM
Author: strmrdr

Date: 3/9/2008 3:25:54 AM
Author: Garry H (Cut Nut)

Date: 3/8/2008 8:41:16 PM
Author: strmrdr
small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

I think you would see it easily Storm

in a bezel yea in a high 4 prong it would be harder too see.

Question..., how would this C & P combination look ''virtually'' if the lgf''s would be painted and shortened and to 70%?

you can improve it, but not save its life DG
And by improving it GIA would bing you for ''brillianteering''

If it gets improved and at the same time gets "binged" for brillianteering...,

, why? Because of the lgf''s length? (out of EX parameters?)

Garry..., what if this Dia. had a 54% table? Would it be improved even more?

 

[Garry H (Cut Nut)]

Date: 3/9/2008 4:37:40 AM
Author: DiaGem

Date: 3/9/2008 4:29:31 AM
Author: Garry H (Cut Nut)

Date: 3/9/2008 4:23:06 AM
Author: DiaGem

Date: 3/9/2008 3:47:41 AM
Author: strmrdr

Date: 3/9/2008 3:25:54 AM
Author: Garry H (Cut Nut)

Date: 3/8/2008 8:41:16 PM
Author: strmrdr
small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

I think you would see it easily Storm

in a bezel yea in a high 4 prong it would be harder too see.

Question..., how would this C & P combination look ''virtually'' if the lgf''s would be painted and shortened and to 70%?

you can improve it, but not save its life DG
And by improving it GIA would bing you for ''brillianteering''

If it gets improved and at the same time gets ''binged'' for brillianteering...,

, why? Because of the lgf''s length? (out of EX parameters?)

Garry..., what if this Dia. had a 54% table? Would it be improved even more?

Dinged, not binged

GIA have a 1 size fits all brilanteering (painting and digging) rule - even if it helps the appearance of the stone.
54% would help, but the proportoins problem can not be made good by FAQ Pricescope standards with anything other than a pavilion or crown angle lowering.

 

[diagem]

Date: 3/9/2008 6:34:48 AM
Author: Garry H (Cut Nut)

Date: 3/9/2008 4:37:40 AM
Author: DiaGem

Date: 3/9/2008 4:29:31 AM
Author: Garry H (Cut Nut)

Date: 3/9/2008 4:23:06 AM
Author: DiaGem

Date: 3/9/2008 3:47:41 AM
Author: strmrdr

Date: 3/9/2008 3:25:54 AM
Author: Garry H (Cut Nut)

Date: 3/8/2008 8:41:16 PM
Author: strmrdr
small ring of death that while it decreases performance is likely not 2 eye visible to a large degree.
Its on the extreme edge of GIA EX and not something id buy.
The predicted AGS score is 5
This is the problem with simple number based systems on top of an imperfect observation based grading system with the trade doing the observation.

I think you would see it easily Storm

in a bezel yea in a high 4 prong it would be harder too see.

Question..., how would this C & P combination look ''virtually'' if the lgf''s would be painted and shortened and to 70%?

you can improve it, but not save its life DG
And by improving it GIA would bing you for ''brillianteering''

If it gets improved and at the same time gets ''binged'' for brillianteering...,

, why? Because of the lgf''s length? (out of EX parameters?)

Garry..., what if this Dia. had a 54% table? Would it be improved even more?

Dinged, not binged

GIA have a 1 size fits all brilanteering (painting and digging) rule - even if it helps the appearance of the stone.
54% would help, but the proportoins problem can not be made good by FAQ Pricescope standards with anything other than a pavilion or crown angle lowering.

Why..., do you think C33.5 combined with P41.8 is too much of a problematic proportion?
I know 41.8 is deep..., but it should be good with a certain CA? Maybe 33 deg. (or shallower?)

 

[strmrdr]

Date: 3/9/2008 7:33:27 AM
Author: DiaGem
Why..., do you think C33.5 combined with P41.8 is too much of a problematic proportion?
I know 41.8 is deep..., but it should be good with a certain CA? Maybe 33 deg. (or shallower?)

c of 31.2 too 31.5 would bring it into a potential AGS1with a marginal for durability girdle(thin girdle shallow crown combo), with a med girdle it would never get below ags3 getting dinged for spread.

 

[diagem]

Date: 3/9/2008 8:57:48 AM
Author: strmrdr

Date: 3/9/2008 7:33:27 AM
Author: DiaGem
Why..., do you think C33.5 combined with P41.8 is too much of a problematic proportion?
I know 41.8 is deep..., but it should be good with a certain CA? Maybe 33 deg. (or shallower?)

c of 31.2 too 31.5 would bring it into a potential AGS1with a marginal for durability girdle(thin girdle shallow crown combo), with a med girdle it would never get below ags3 getting dinged for spread.

Even though a C33.5, P41.8, lgf''s @ 70%, 54%T would probably be a better looking stone than any 31.5-2 degree crown?

 

[strmrdr]

Date: 3/9/2008 9:38:23 AM
Author: DiaGem
Even though a C33.5, P41.8, lgf''s @ 70%, 54%T would probably be a better looking stone than any 31.5-2 degree crown?

Would need some painting too bring the uppers in and would get kicked down on contrast.
The cutting charts are useless for this combo and it would have too be ran in the software but im guessing somewhere around ags6 with no painting....

 

[strmrdr]

41.8/30/54/70 would make ags1 maybe... again it would have too be ran in the software...

 

[diagem]

Date: 3/9/2008 10:06:37 AM
Author: strmrdr

Date: 3/9/2008 9:38:23 AM
Author: DiaGem
Even though a C33.5, P41.8, lgf''s @ 70%, 54%T would probably be a better looking stone than any 31.5-2 degree crown?

Would need some painting too bring the uppers in and would get kicked down on contrast.
The cutting charts are useless for this combo and it would have too be ran in the software but im guessing somewhere around ags6 with no painting....

Storm..., please paint the lgf''s and show me a face-up of a virtual Diamond in office lighting or any other...

 

[strmrdr]

33.5/41.8/54/70 crown painted

GIA would downgrade this level of painting too VG, AGS might or might not downgrade it.
But it would take a hit for spread and contrast anyway. Maybe AGS3?

 

[strmrdr]

lowers painted, both ags and gia would hammer this much lower painting most likely.

 

[strmrdr]

Same lighting Garry used above and the same I use too show asscher patterns which is worst case with rounds.

 

[strmrdr]

crown painting comparison.

 

[strmrdr]

dc office lighting crown painting

 

[strmrdr]

dc office lowers painted both 41.8p 33.5c 54T 70lgf

 

[diagem]

Date: 3/9/2008 10:34:15 AM
Author: strmrdr
dc office lowers painted both 41.8p 33.5c 54T 70lgf

How is going to look with a 40.8 P (not painted)? I guess much better!

 

[strmrdr]

here ya go... ags1 takes a hit in dispersion due too the shallow upper girdles most likely.