Explanation of GIA lab report notation

[buzzf]

What does the comment "Cut grade is based on brillianteering of the half-facets" mean??

 

[RockDoc]

GIA''s cut grading of stones is new.

I would suggest you call the lab and ask what the meaning is..then tell us what they said and you''ll get educated opinion as to how good their explanation is.

They have a toll free number : 1-800-421-7250

Rockdoc

 

[JohnQuixote]

Nice short answer from Bill. I'd be interested in hearing what they tell you.

Long answer discussed here: https://www.pricescope.com/community/threads/consumer-advisory-gia-cut-grade-rounding-problems.39401/

 

[Garry H (Cut Nut)]

Would love to see a scan of the report?

 

[valeria101]

Date: 2/11/2006 2:25:11 PM
Author:buzzf

What does the comment 'Cut grade is based on brillianteering of the half-facets' mean??

'Guess literally it means that the cut grade took into account that some 'twisting' (look up 'painting' and 'digging', either a controlled modification of azimuth) of the upper girdle facets. Usually this would be done to improve brilliance while keeping weight loss to a minimum. As far as I know, GIA doesn't quite like this for unknown reasons - so if the cut grade is rather low on this diamond, it may be a top notch one that managed to fall between the lines of (the still green) GIA cut grading system.

Anyway, hard to tell before at least a copy of the report gets posted, because these cut grades are new and it looks like few with such comments were released.

Peter Yantzer of AGS wrote THIS about what this mysterious 'brillianteering of the halves' does to a diamond with otherwise undisputed top cut marks.

GIA also has a neat document explaining how this brillianteering thing is judged by its cut grading (PDF here from a link of the FacetWare site).

If you don't quit half way reading that (I did - a couple of times!) it may become apparent from the two relatively tiny pieces of literature (3-4 pages one, 6 the other) that one lab likes their diamonds twisted and the other can't handle that. The first article talks about joint effects of brillianteering (better light return, better size/weight ratio and better weight retention in the same time) while the other gives overwhelming weight to... weight retention and buries the other two appealing points in the sand.

My 2c


This subtle divergence of opinion between two major diamond grading labs... is why everyone wants to see a copy of that report so badly!

The long-winded thread 'John Quixote' linked in his post goes into subtle detail of these things on a super steep learning curve

.


Thanks in advance for considering to post it... Please ?

 

[JohnQuixote]

Great links Ana.

 

[DiamondExpert]

Ana - once again, my hat''s off to you on the LINKS!...have you thought of burning your database of colored gems and diamonds on a CD for distribution?!?

Thanks!

 

[WinkHPD]

Yes, please, but only if you provide your succint and on the money comments after each article. I absolutely loved your analysis of the differing opinions on this by the two labs. One taking the time to analyse the differing types and directions and the resultant affect on the brilliance and beauty of the stones and the other just saying, well, heck this is too hard to analyse, it must be bad...

Wink

 

[buzzf]

I don''t have a scanner.
Here is info from report:
GIA #14799340
measurements 7.80 - 7.83 x 4.76
round brilliant
1.70 carat
color H
clarity vs2
cut grade: very good
Finish:
polish excellent
symmetry very good
fluoresence none

table 55%
crown angle 34.5 15.5%
pavilion angle 40.8 43.0%
total depth 60.6
girdle thin to medium faceted
there is a lower pavilian measurment of 80% and a measurement in the crown area of what appears to be 65 or 6.5 - it''s blurred
Does this help?


I put it through the HCA and got exc for light return, fire and scintillation; very good for spread.

With the comment on brillianteering - should I keep looking, or is this a good buy. The price is $15,500.

The lady at GIA said the comment refered to lowering of cut grade from excellent to very good because of facet lines not being sharp.

Thanks for any comments you can give me.

 

[Garry H (Cut Nut)]

The polish is excellent so it does not mean the facets are rounded.

It seems as John Q suggested - the stone has a tricked girdle - re some of the coments and links made above.

It is likley that this is a cracker jack stone and the fact that GIA do not know how to grade it would not worry me.
To be sure if you can get us an ideal-scope photo (here is how to do it very simply http://www.ideal-scope.com/newsletters_issue008.asp ) or at least look at it yourself thru one - you can identify the pattern we expect it to have from the links given above.

 

[varroa]

Here is a cert. Tell me what you think the brillianteering is in this case? Painting, digging...??