Symmetry grades and IdealScope images mismatched?

[user_jason]

I recently had 3 IdealScope images done through James Allen. The results seem counter intuitive to me, because the stone with the worst symmetry has an almost perfectly symmetrical IdealScope image. Could there be a mixup?

(Note: I want to be clear I'm NOT suggesting JA intentionally mixed up these images.)

Stone 1 (my fave): 1.74 FVS2, ideal cut, vg symmetry, ex polish, faint flour


Stone 2: 1.76 GVS2, ideal cut, ex sym, ex polish, no flour, ~1,500 savings over Stone 1


Stone 3: 1.70 GVS1, vg cut, ex sym, ex polish, faint flour, ~1,500 savings over Stone 1


Any advice is appreciated!

 

[04diamond<3]

I LOVE THIS!!!!!!!!!!!!!!!!!!!!!!!! The first one, and YES WITH VERY GOOD SYMMETRY is obviously the superior stone! If you're curious about it, you can always verify with JA, but honestly, it is nearly perfect!!! Love the fat arrows and no leakage!

 

[JulieN]

You need to post the link to the diamond in order to match up the IS to the video/GIA report, to see if there is a mix up or not. It happens sometimes.

 

[diamondloveaffair]

I hardly doubt the stones got mixed up. The way gia defines symmetry isn't the same as you defined it.

 

[user_jason]

04diamond<3 - Thanks! Love the enthusiasm. I definitely dig Stone 1 the most, but was just paranoid since I expected it to be a bit asymmetrical (and like another poster alluded to, I may not fully understand the GIA definition of symmetry).

JulieN, here are the links:
Stone 1: http://www.gia.edu/cs/Satellite?pag...&c=Page&cid=1355954554547&reportno=5136353051
Stone 2: http://www.gia.edu/cs/Satellite?pag...&c=Page&cid=1355954554547&reportno=2146178310
Stone 3: http://www.gia.edu/cs/Satellite?pag...&c=Page&cid=1355954554547&reportno=6112978694

Thanks diamondloveaffair! And thanks for the feedback on my previous post on Stone 1: https://www.pricescope.com/community/threads/small-table-54-concerns.187923/

 

[yssie]

I recently had 3 IdealScope images done through James Allen. The results seem counter intuitive to me, because the stone with the worst symmetry has an almost perfectly symmetrical IdealScope image. Could there be a mixup?

Pattern of the arrows in these light reflector tools is optical symmetry.
Symmetry dictated on the report is physical "facet-meet" symmetry - symmetry of how the 57 facets cut into the stone meet up, etc.

Optical symmetry is the pattern of reflections, reflections of reflections within the stone. It IS a function of "facet-meet" symmetry to the extent that if the actual, physical facets are totally out of whack you're going to see the effects in the primary and tertiary reflections, but it's very possible to have decent optical symmetry w/ a less-than-top symmetry grade on the report because of the various ways the labs can downgrade symmetry and the effects they may (or may not, rather) have on optical symmetry. And it's very possible to have less-than-fantastic optical symmetry in a stone graded EX or 0 for symmetry. And to judge symmetry IS images like these are very blunt tools anyway - the second pic isn't actually directly face-up, for example, largely negating the usefulness of any discussion on minute artifacts... there was a Crafted by Infinity RB w/ picture perfect H&A and VG symmetry by the report floating around a couple of years ago...


Here is an outline of how GIA defines and grades symmetry: http://www.diamondcut.gia.edu/pdf/polish_and_symmetry.pdf


ETA: third stone looks painted and table/pav look okay by the pic - why did it get the VG cut grade? I can't see your links - can you post the report number and exact ct weight (x.xx)?

 

[denverappraiser]

I suspect it's either the wrong image for the stone or an error at GIA. Ask the folks at JA to take a look.

Symmetry grading at GIA is a demerit system. This means that all stones start out with the assumption of 'excellent' and then get dinged for various things that are present. Some of these things are pretty tiny details but they're having the table or culet off center, the table not parallel to the girdle, a mismatch on the crown & pavilion mains, etc. Nearly all will turn up in an IS image. The only thing I see in this one is that it looks like the culet is a little off center to the table but this may be an artifact of the photography, not the stone (you'll notice image #2 has the same visual problem and it graded 'excellent. That one surely is an issue with the picture').

This is an area where what GIA does in the lab and what they teach in the school are different by the way. A few years ago I believe that symmetry grading moved from being done by a gemologist to being done by an automated system. I don't know all of the rules for the program and things like the boundary from ex to vg can and do change without notice. That's one of the problems of being a 'field' gemologist where you are expected to keep up with a moving target.

 

[user_jason]

Thanks Yssie! Very helpful symmetry info! Here's the GIA #s and carat you requested:
Stone 1: 5136353051, 1.74
Stone 2: 2146178310, 1.76
Stone 3: 6112978694, 1.70

denverappraiser, interesting that, it could be the quality of the images taken. I would guess that JA would be doing these constantly and would be quite proficient, but perhaps you're right that it's a poor quality image. FWIW, they all have sub 2 HCAs so I expected fairly good images for all of them. Thank you for the feedback!

 

[SFFaithful]

The Ideal Scope on #1 looks great. I'm getting scopes from JA soon too and hope the ones I picked look just as good as the scope on #1

 

[JulieN]

IS #3 matches with GIA #3, easy to tell with the brillianteering.

IS #2 has a bigger table than IS #1, which corresponds with the GIA reports.