Question on GIA ExExEx

[Owies Nana]

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]

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]

yes, numbers are numbers. you want to make sure it looks good on the image too

 

[Dreamer_D]

Depends how obsessive you are. I think for many consumers, GIA Ex plus a good HCA is enough assurance of a good looking diamond.

 

[yssie]

https://www.pricescope.com/journal/laboratory_cut_grades_what_report_doesn%E2%80%99t_show

 

[Dreamer_D]

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]

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

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 - 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_D]

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

 

[yssie]

Face on photo could even be sufficient for both, wouldn't recommend going by numbers though:

both 33.5/40.6/58

 

[Owies Nana]

Here is the image of the GIA ExExEx I asked about. Thoughts?

 

[Owies Nana]

Deleted post.

 

[0-0-0]

Do you have the specs and report number?

I think the IS shows slight leakage under the table.

 

[Owies Nana]

Don't want to identify any more than this due to lurkers.

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

It scores a 1.4 on HCA.

 

[yssie]

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]

Thanks, Yssie.

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

 

[Gibson486]

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]

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]

The girdle is irregular: thin to slightly thick. How will this impact the performance of the stone?

 

[stone-cold11]

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]

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?

 

[Gibson486]

over 4 cts? I do not think any lurkers would be taking that stone....

 

[yssie]

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]

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]

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_D]

I think it looks good, especially given the rarity of well cut ginormous stones

 

[Dreamer_D]

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.

 

[Owies Nana]

Neither of these photos is mine.

Mine is the third IS picture.

 

[diamondseeker2006]

over 4 cts? I do not think any lurkers would be taking that stone....

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

 

[yssie]

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..

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_D]

Neither of these photos is mine.

Mine is the third IS picture.

I know honey! I was just poking at Yssie some more.