GIA''s Ex Cut grade was determined through observation testing which common folks like you and me looked at to determine which appearance pleased their eyes the most. Of the GIA Ex''s I have seen on both ends of their spectrum (and in the middle for that matter), they''ve all shown excellent brightness, fire and scintillation. Granted I haven''t seen stones that fell on the very fringes of the Ex grade but I have seen and possess stones that fall on the fringes/outskirts of the Very Good grade bordering on the Ex grade so in answre to your 2nd question...
Definitely.
Each lab has incorporated different criteria in determining their cut grade. GIA, after working with ray trace technologies abandoned it since it didn''t always correllate with human observation and turned solely to human observation testing alone. The logic behind their system is that the most important technology the consumer walks away with after its all said and done *are their eyes*. So human perception of diamond beauty took precedence in determining the grading system. There had to be differences between the grades that were notable to human vision. AGS''s Cut Grading system is based on advanced ray trace analysis and determination on where a diamond is drawing its light from in common viewing conditions through the "angular spectrum" observerable through their ASET technology coupled with proprietary "Performance Grading Software" which performs the ray trace examination. In some ways the AGS system is more critical in its examination than the GIA''s but then there are also instances where an AGS 1 (or even higher) can be brighter than an AGS 0. It can get complicated which is why I prefer to stick with stones that get the highest grades in both systems.
It all depends on what the definition is of good performance. Many experts claim that there are various levels of quality within the EX-grade, and it depends on where your threshold is for ''good performance, whether the stones on the fringes of the EX-grade are still considered good enough performance for you.
Not always. In the same way, you sometimes cannot tell the difference between a specific D and a specific E-colour. Or between a specific VS2 and a specific SI1.
No sweat Jayrenay. I certainly wish I had more time I could devote to answering questions on this forum. It''s a little tough to break away sometimes. Always a pleasure to serve.Date: 11/3/2006 11:44:09 PM
Author: jayrenay9
Thanks for answering the queston Rhino -- it''s really appreciated! I asked the question in another thread and apparently my common sense isn''t commonWhatever that was supposed to mean, I suppose I don''t get it due to my lack of common sense.
Thanks again,
jayrenay
As Paul said it depends on how you define good.
As usual, Paul nailed it. It depends on what you call a top performer. GIA excellent means that there’s a pretty good chance that the stone is in the top 20% or so according to GIA’s rules. Some would argue that it’s even more generous than that because it doesn’t seem to be a linear scale so maybe it’s more like the top 30-40%. Even that is sort of a problem for shoppers if you don’t happen to agree with their criteria.
Sorry for the confusion there. It started on another thread where I asked what difference one would see in an ex/ex stone compared to a gd/gd stone. Gary (Cut Nut) responded back "common sense isn't always common." I'm not sure exactly what he meant, but I took it that if I had common sense I would know the answer to that question. Maybe I read it wrong. All I know, is that I still had no idea what the difference would be -- whether I have common sense or not.Date: 11/4/2006 11:41:27 AM
Author: Rhino
No sweat Jayrenay. I certainly wish I had more time I could devote to answering questions on this forum. It's a little tough to break away sometimes. Always a pleasure to serve.Date: 11/3/2006 11:44:09 PM
Author: jayrenay9
Thanks for answering the queston Rhino -- it's really appreciated! I asked the question in another thread and apparently my common sense isn't commonWhatever that was supposed to mean, I suppose I don't get it due to my lack of common sense.
Thanks again,
jayrenay
I don't quite get your statement that 'your common sense isn't common' but if its regarding your diamond preferences ... you can't let anyone dictate to you what you do and don't like. Oftentimes people (including myself) like to impose our preferences on others when their tastes and preferences may be totally different. I'm not sure if that even addresses what you're talking about but ... I'm taking a stab in the dark there. Your common sense is YOUR common sense and I'm sure it's working just fine even if its not common.
There are many combos I like and some I don''t like that others like.
Same problem Storm - you are designing a grading system using criteria that were not available when the systems we have now were invented.
Garry I agree in some ways disagree in others.
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