AGS Symmetry Grading Question

[TheBachelor]

Can anyone tell me how AGS determines its symmetry and proportion grades? What exactly do they refer to?

Is symmetry based on a Sarin report that shows all the crown and pavilion angles. I''ve heard the angles on the AGS report are an average of all the individual angles, is this true? Would the symmetry grade correlate to some +- percentage from that average? What does the proportion grade refer to?

Assuming a diamond has an AGS0 Cut Grade, (Ideal Polish, Symmetry and Proportion), what does this tell me about the diamond compared to one with Good Symmetry or Proportion?

Is there an AGS web page that explains all of this?

Thanks

 

[TheBachelor]

I thought my question was relevent to the purchases of many on this site, but I guess it wasn't due to the lack of responses.

Maybe I could rephrase it.

My main question is about the AGS cut symmetry and proprotion grading information I've seen. I havent seen any definitive info about how they arrive at those grades. I asked a question about how AGS arrives at a proportion or symmetry grade and didnt get an answer, so I figured I would check their web site. Maybe I was lazy asking the question here instead of checking with the ultimate source.

To my surprise, I didnt find the info I was looking for there. Their consumer info seemed to try to convince me to rely on an ags report rather than explain it to me. My feeling is that it might be more of a tool for sellers of diamonds than a tool for buyers of diamonds.

I did a little more searching and found on the GoodOldGold site an explaination of the Megascope and "Advance External Cut Analysis" From what I read there, it seems that tolerances of the various angles is what matters when analyzing cut angles. There are examples there that show diamonds with crown and pavillion angles that are very close to each other.

So, that gets back to my question. How does the AGS ideal proporation and symmetry correlate to crown and pavillon angles that are very close to each other.

Also, here is a quote apparently from an AGS ad on goodoldgold.com. http://www.goodoldgold.com/hearts_and_arrows.htm Maybe its not an AGS ad, but there is an AGS cert in the ad: "Symmetry -- Every facet needs to be of equal size and perfectly opposite it's counterpart on the crown and pavillion"

That is a very strong statement. I was a Math major, so to me, equal means equal, not approximately. Perfectly, requires even more perfection than I have seen in most things in life. Is this simply advertising jargon or what?

I am about to buy an AGS000 diamond. Can I expect that statement to be true? Will I get a diamond where every facet needs to be of equal size and perfectly opposite it's counterpart on the crown and pavillion?

 

[Garry H (Cut Nut)]

Labs grade from Sarin (like Megascope) reports and with human observers making subjective assessment of facet meet points.

If you want the best results use H&A's and Ideal-Scope viewers - even if facets do not meet - the facet alignment can not cheat a visual assessment aid. Labs do not use these instruments - they are a bit slow to change.

Read the tutorial here too so you know which AGS 0's to avoid.

 

[justme]

forgot link see below

 

[justme]

If you are looking for the actually dimensions that correlate with the AGS grading scale, this link is most complete list that I've found.

http://www.1diamond.com/diamonds/ags-class.htm

That said without corroboration from "those that know" I can't say that it's accurate. Maybe 'those that know' could confirm.

Justme

 

[Richard Sherwood]

-----------
Can anyone tell me how AGS determines its symmetry
and proportion grades? What exactly do they refer to?
-----------

Bach, probably the reason you're not getting many replies is because your question involves a labor intensive post in reply.

For the proportion part of your question, the site recommended is good, along with http://www.diamondgrading.com/Articles_GIA_vs_AGS_CUT.htm

For the symmetry portion of your question, a good site is http://www.duke.edu/~apierce/interests/diamonds.html

Not all aspects of symmetry is covered in that site, but enough to give you the general idea.