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Question on GIA ExExEx

Owies Nana

Shiny_Rock
Joined
May 16, 2010
Messages
394
If a stone is a GIA ExExEx and scores 1.4 on HCA, is it necessary (or beneficial) to get IS or ASET image?
 

Karl_K

Super_Ideal_Rock
Trade
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Aug 4, 2008
Messages
10,028
yes it is a good idea because the numbers only tell part of the story and they are averaged then rounded.
Images tell you more of the story.
 

minmin001

Ideal_Rock
Joined
Mar 21, 2011
Messages
2,047
yes, numbers are numbers. you want to make sure it looks good on the image too
 

dreamer_dachsie

Super_Ideal_Rock
Joined
Dec 16, 2007
Messages
24,364
Depends how obsessive you are. I think for many consumers, GIA Ex plus a good HCA is enough assurance of a good looking diamond.
 

dreamer_dachsie

Super_Ideal_Rock
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Messages
24,364
Yssie|1304982881|2916768 said:
https://www.pricescope.com/journal/laboratory_cut_grades_what_report_doesn%E2%80%99t_show
Nice article. The photos of the different diamonds that meet GIA Ex were really telling. But would the HCA not add further contraints to the pool of possibles, eliminating some of the less optimal cuts?
 

yssie

Super_Ideal_Rock
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Dreamer_D|1304983089|2916773 said:
Yssie|1304982881|2916768 said:
https://www.pricescope.com/journal/laboratory_cut_grades_what_report_doesn%E2%80%99t_show
Nice article. The photos of the different diamonds that meet GIA Ex were really telling. But would the HCA not add further contraints to the pool of possibles, eliminating some of the less optimal cuts?

I think it's safe to say that for the vast majority of consumers even just GIA EX would be a safe improvement 8)

That said, we know that HCA is equally kind to shallow combos that I would consider too shallow for a ring and harsh on steeper combos that are often beautiful stones IRL. I get why some sorts of constraints are needed - it's a blunt, fast tool, and efficiency and precision are contradictory goals, and since the HCA is designed to vet stones for all sorts of jewellery - rings, earrings, pendants, navel rings :cheeky: - unless the user reads all the fine print the nuances go unnoticed, and most don't.

So if HCA + GIA EX narrows it down to a pool of A)very nice B)disablingly asymmetric C)overly shallow stones, the catch being that by using HCA + GIA EX you're missing out on some nice ones that HCA considers too deep - but that's a tradeoff that's worth the time for most people we see on RT in a hurry and on a budget, then there are other tools to further narrow from there, and of course plenty of people on RT can help with that. But I do think it's important that consumers recognise that *if* getting a certain type of stone is important to them, they shouldn't skimp on that last step of checking for B & C.
 

dreamer_dachsie

Super_Ideal_Rock
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24,364
B can be judged (broadly) with a simple face on photo, and C can be judged from the GIA cert, no?
 

yssie

Super_Ideal_Rock
Premium
Joined
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20,749
Face on photo could even be sufficient for both, wouldn't recommend going by numbers though:

both 33.5/40.6/58
AA_1.jpg
BB_1.jpg
 

thbmok

Brilliant_Rock
Joined
Jul 30, 2010
Messages
891
Do you have the specs and report number?

I think the IS shows slight leakage under the table.
 

Owies Nana

Shiny_Rock
Joined
May 16, 2010
Messages
394
Don't want to identify any more than this due to lurkers. :roll:

Specs:
Depth 60.4%
Table: 58%
Crown Angle: 34 degrees
Pavillion Angle: 41 degrees

It scores a 1.4 on HCA.
 

yssie

Super_Ideal_Rock
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Think it'll be a nice one IRL :))

A lot of the minutiae we might point out on here is lost in practical translation, esp. since you're always looking at it with two eyes..
 

Owies Nana

Shiny_Rock
Joined
May 16, 2010
Messages
394
Thanks, Yssie.

I always enjoy your posts, and since this is a BIG purchase ( :naughty: hint, hint), I appreciate your input.
 

Gibson486

Rough_Rock
Joined
Dec 28, 2010
Messages
91
That scope image looks good. if the diamond is in your budget, then this looks like it could be a good choice. Just buy it and see if it speaks to you.
 

Stone-cold11

Super_Ideal_Rock
Joined
Sep 9, 2008
Messages
14,069
Diamond is probably too far into the idealscope when that image is taken, arrowheads starting to become paddles.

What is the girdle variation?
 

Owies Nana

Shiny_Rock
Joined
May 16, 2010
Messages
394
The girdle is irregular: thin to slightly thick. How will this impact the performance of the stone?
 

Stone-cold11

Super_Ideal_Rock
Joined
Sep 9, 2008
Messages
14,069
Not affecting performance, just slightly low total depth for that combination, might have a very/extremely thin girdle that might pose a chipping risk, depending on where/how extensive it is and how it is set.

Thin - slightly thick should be fine. Still weird that it can get a slightly thick girdle.

What size is the stone?
 

Owies Nana

Shiny_Rock
Joined
May 16, 2010
Messages
394
The stone is over four carats, so I am guessing a larger diameter allows for more variation in the girdle thickness?

Will setting it in prongs be an issue?
 

yssie

Super_Ideal_Rock
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Owies Nana|1305034059|2917283 said:
The stone is over four carats, so I am guessing a larger diameter allows for more variation in the girdle thickness?

Will setting it in prongs be an issue?

Not SC obviously, but girdle thickness is measured as a percentage of diametre - thin, med, sl thick are all ranges of allowable thicknesses. GIA measures girdle thickness in the valleys (only) - so the thinnest valley region has a mm measurement that falls into the "thin" range and the thickest valley in the sl thk range.

Since your stone is larger you have even less to worry about wrt setting/wearing - even the thin portion will be considerably wider than on a sub-1carater, should be just fine in prongs.

Ditto PP - wouldn't worry too much about lurkers poaching that one, btw. It's much, much harder to find large stones that are well cut - the loss of even a little weight in these sizes can drastically affect value - so cutters have more incentive to preserve a little extra in the pavilion, in the girdle... overall your pool of choices is so much smaller, I'd say this one is a lucky find!
 

Stone-cold11

Super_Ideal_Rock
Joined
Sep 9, 2008
Messages
14,069
Not large diameter. The large table with that crown angle usually have depth in the 61% range instead of low 60% range.

Such a large stone is fine with thin girdle, as that is a % of the diameter, it could easily have the same girdle thickness, in mm, of a medium girdle thickness 1 carat stone.
 

Jim Summa

Shiny_Rock
Trade
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Sep 9, 2009
Messages
176
I agree with what stone-cold mentions, it is likely that the image was taken with the stone too high in the ideal-scope. It is easy to do because the stone’s a little larger than what is commonly seen, at 4 cts.


To take a IS-image, the girdle of the stone needs to be level with the base of the ideal-scope. If one does not adjust the base, a bigger stone sticks out higher into the ideal-scope and it has an effect on the image. On the one side, the black areas of obstruction could become bigger than in a properly taken image. On the other hand, areas of light leakage might be hidden. In other words, it would be best to shoot again to make sure it is what it is.
 

dreamer_dachsie

Super_Ideal_Rock
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Dec 16, 2007
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24,364
I think it looks good, especially given the rarity of well cut ginormous stones :rodent:
 

dreamer_dachsie

Super_Ideal_Rock
Joined
Dec 16, 2007
Messages
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Yssie|1304991164|2916914 said:
Face on photo could even be sufficient for both, wouldn't recommend going by numbers though:

both 33.5/40.6/58
AA_1.jpg
BB_1.jpg
And they are both GIA Ex with HCA under 2?

I like a face up photo for this reason, you can tell a lot.
 

diamondseeker2006

Super_Ideal_Rock
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Jan 11, 2006
Messages
55,806
Gibson486|1305034419|2917288 said:
over 4 cts? I do not think any lurkers would be taking that stone....
:lol:

The stone looks great! PLEASE come back and show us pictures when you get it! :appl:
 

yssie

Super_Ideal_Rock
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20,749
Dreamer_D|1305051425|2917542 said:
Yssie|1304991164|2916914 said:
Face on photo could even be sufficient for both, wouldn't recommend going by numbers though:

both 33.5/40.6/58

And they are both GIA Ex with HCA under 2?

I like a face up photo for this reason, you can tell a lot.

Yeah, I like those examples - numbers on both are virtually identical and yet.. :-o

Doesn't fit the GIA EX + HCA criteria - First one is one of my old stones GIA VG cut, depth 60.3, bottom depth 60.1 - can't find the original thread to see if it had GIA or AGS report..
ETA: [URL='https://www.pricescope.com/community/threads/opinion-on-idealscope-image-please.55984/']https://www.pricescope.com/community/threads/opinion-on-idealscope-image-please.55984/[/URL]
Apparently GIA EX report, facetware vg (2007)
 

dreamer_dachsie

Super_Ideal_Rock
Joined
Dec 16, 2007
Messages
24,364
Owies Nana|1305052485|2917559 said:
Neither of these photos is mine.

Mine is the third IS picture.
I know honey! I was just poking at Yssie some more.
 
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