AGS 0 vs. GIA "excellent"

[GeoAtl]

First, thank you all so very much for all the help and the information I have been able to glean from this rather incredible forum. I think I am down to two stones and am having some trouble figuring out how to choose between them (the original thread can be found here: https://www.pricescope.com/community/threads/round-brilliant-question.43143/).

1) round brilliant, new (2006) AGS 0, 1.22ct, eye clean SI2, H, 6.83 - 6.87 x 4.24mm, negligible fluorescence, 61.9 depth, 56.1 table, 40.8 pavilion angle, 35.4% crown angle and 15.3% crown %, 2.4 HCA.

2) round brilliant, new GIA "excellent cut," 1.23ct, eye clean SI1, I, excellent polish, very good symmetry, 61.1 depth, 56 table, 33.5 crown angle, 41 pavilion angle, no fluorescence, HCA score of 1.

The price of the two stones is within $150 or $200 of each other (the first stone is the more expensive one) and they are both virtual, so there is no way for the vendor to take a look at them for me or to run any other tests on them. Which one would you go with?

From the thread above, I understand and very much appreciate Bill and John's comments about the preference to see each diamond in person but am just not sure that even magnified pictures would provide that much guidance here. The best alternative would be to do the real world test, but in its absence (isn't it the way all the online vendors operate?), I guess I have no choice but to rely on the stats above.

 

[belle]

if there is no way for the vendor to look at them, how do you know they are eye clean?
also, are the crown/pavilion numbers angles or percentages?

 

[Rod]

Hi......

Someone has to see the stones in person to help guide you. The vendor should be able to call these virtual stones in-house and give you their expert opinion. I like the HCA of the GIA graded stone. Still, one should not buy a stone based on numbers alone.

Are you up against a time crunch that will not permit having the vendor bring the stones in to be seen? Are you dealing with a PS vendor? If you are, I''m pretty confident they can call the stones in and give you expert help.

Good Luck.........

 

[GeoAtl]

Belle, the crown/pavillion numbers are angles (I''ve updated my original message to show this). The wholesalers have assured my vendor (it is a PS vendor) that both stones are eye clean. The vendor knows the wholesalers and says that he trusts them.

 

[GeoAtl]

Date: 4/10/2006 3:26:46 PM
Author: Rod
Hi......

Someone has to see the stones in person to help guide you. The vendor should be able to call these virtual stones in-house and give you their expert opinion. I like the HCA of the GIA graded stone. Still, one should not buy a stone based on numbers alone.

Are you up against a time crunch that will not permit having the vendor bring the stones in to be seen? Are you dealing with a PS vendor? If you are, I''m pretty confident they can call the stones in and give you expert help.

Good Luck.........

What type of guidance or meaningful information should I request/expect from this PS vendor? Even if it is able to get the stones in, I fully expect it to tell me that they are both beautiful and that the final decision is mine. Can you please tell me what other information a vendor can provide to help me make the decision?

 

[valeria101]

The cut grades are not 'equivalent' - the two labs accept different ranges of proportions in their top cut grade (GIA's is wider, but they do not overlap completely, so one can't say that AGS0 is a subset of the GIA Ex range). And there are other factors involved too... perhaps I didn't dig as much into the meaning of those, mostly 'cause the divergence about what proportions are 'in' and 'out' is quite striking anyway.


SI1 sounds better

because it is SI1. And I'd rather trust Garry's word on cut (i.e. the HCA system) to choose between these.

 

[Rod]

Well for one, as a PS vendor they can view these stones through a ideal scope. And they're far better experts at diamond performance than most of us layperson's and for the tidy sum of money you're looking to spend, I would want the assurance that they've seen the stones and can honestly report their characteristics to you. Remember, mother earth baked these puppies up. A mammal cut them, and no two, even two with almost identical proportions will be exactly the same.

I wish you nothing but good success, but I would want to ensure that before I spent my money, an expert saw the diamonds and could share their expert opinion. Chances are, they're both beautiful, but I would want that assurance before I spent my money.

Best wishes.........

 

[belle]

Date: 4/10/2006 3:36:18 PM
Author: GeoAtl
Belle, the crown/pavillion numbers are angles (I''ve updated my original message to show this). The wholesalers have assured my vendor (it is a PS vendor) that both stones are eye clean. The vendor knows the wholesalers and says that he trusts them.

very good. most ps vendors do have the capabilities to take idealscope images. i would take advantage of this. there is very good information that can be garnered about a diamond with a good idealscope image. you can easily determine optical symmetry and minor facet configurations, which play a significant role in the appearance and performance.

 

[GeoAtl]

At this point, I''ve discussed different stones with three (3) different PS vendors and they have all told me that they do not have the equipment to examine the stones. They''ve all strongly encouraged me and I fully intend to take my final selection to an independent appraiser to confirm the cert. I have spoken with 2 local PS appraisers here, whose offices have told me that they do not, for instance, have Ideal Scope and would only be able to confirm that the stones match the certificate but would not be able to run any additional advanced tests on them.

 

[belle]

Date: 4/10/2006 3:59:36 PM
Author: GeoAtl
At this point, I''ve discussed different stones with three (3) different PS vendors and they have all told me that they do not have the equipment to examine the stones. They''ve all strongly encouraged me and I fully intend to take my final selection to an independent appraiser to confirm the cert. I have spoken with 2 local PS appraisers here, whose offices have told me that they do not, for instance, have Ideal Scope and would only be able to confirm that the stones match the certificate but would not be able to run any additional advanced tests on them.

3 different ps vendors who don''t have a simple idealscope?
hmmmmmm

you might want to find one that does.

or not. it''s your decision. if you''re comfortable not having that kind of information, then go for it.

 

[Rod]

Date: 4/10/2006 4:05:18 PM
Author: belle

Date: 4/10/2006 3:59:36 PM
Author: GeoAtl
At this point, I''ve discussed different stones with three (3) different PS vendors and they have all told me that they do not have the equipment to examine the stones. They''ve all strongly encouraged me and I fully intend to take my final selection to an independent appraiser to confirm the cert. I have spoken with 2 local PS appraisers here, whose offices have told me that they do not, for instance, have Ideal Scope and would only be able to confirm that the stones match the certificate but would not be able to run any additional advanced tests on them.

3 different ps vendors who don''t have a simple idealscope?
hmmmmmm

you might want to find one that does.

or not. it''s your decision. if you''re comfortable not having that kind of information, then go for it.

I agree with Belle completely. Something doesn''t sound right either that none of these vendors have an idealscope????????? They''re not that expensive. You could buy one yourself.

 

[GeoAtl]

Three vendors: Diamond.com, USA Certed and Blue Nile. The message so far has basically been that unless the wholesaler is in the position to provide additional information to me, these vendors do not provide these additional services (Blue Nile can only do it if it's one of their signature diamonds).

Since I am obviously a complete novice at this (I've read a number of PS threads and tutorials, however), I have absolutely no idea what additional information is considered essential and what information falls in the category of "nice to have" in the context of dealing with new AGS 0 and GIA "excellent" cuts. The information contained in these certs notwithstanding, is it the opinion of the learned PS experts that at least an Ideal Scope picture is a must before a diamond is purchased? What else?

 

[GeoAtl]

Here is one of the reasons I''m so confused: the poster in this thread (https://www.pricescope.com/community/threads/could-this-be-the-one.42739/ was not encouraged to obtain any additional tests/information on her significantly more expensive diamond, so I am just very confused about the difference in recommendations. Can anybody shed some light on this, please?

 

[He Scores]

Geo,

If it would be any help, tell those vendors that if they can provide me the Sarin mfg. report, I could generate a BrayScore for you.



Bill Bray
Diamond cutter

 

[Paul-Antwerp]

Based upon this info, it is impossible to make a choice between these two.

Value-wise: H-SI2 and I-SI1 are equal.

Cut-wise: the AGS-0 is not the greatest combo within AGS-0, but still it has the coveted report (if it is not a newly dated old-style proportions-based report). And the GIA-EX is definitely one of the better GIA-EX''s, and could possibly also get an AGS-0, if submitted there. So, basically, no difference there.

If we need to make a difference, more info is needed. And that is probably impossible to get on a virtual stone. And then, this is very important to understand: not all online-vendors operate in this way, with primarily virtual stones. Many do have a lot of stock in house, and they fight to get a hold of the cherries. These people can easily offer you that extra info, which we seem to be needing now.

Live long,

 

[Garry H (Cut Nut)]

It is a sad thing that you are dealing with big bueracratic dealers.
These companies seem to believe that might is right and refuse to introduce ''free information'' will raise their cost base.

If they wanted to they could take reasonable ideal-scope photo''s with less than $300 for the equipment and no special skill is needed at all:

http://www.ideal-scope.com/newsletters_issue008.asp
Here is the text without the photo''s:

Want to take ideal scope photo''s of diamonds? This newsletter gives you tips with off the shelf digital cameras. Not all cameras are the same, but these tips work with most.

Of the 2 types of digital camera''s, compact and pro-consumer, we find the compact ones much easier to use than the larger ones.

Rule #1 - Use normal auto focus.
Never use macro focus.

Using a Compact Digital

Ideal-light method

Using an Ideal-light, sit the diamond in the hole and simply put the camera on top and take the photo. If you have a pink background like the photo on the left, you will need to adjust the white balance. The ideal-scope sits nicely atop the lens of most compacts because they have a smaller lens.

Buy Ideal-Light for US$30

For professional results, use this system

White Balance Control

Change the White Balance to “Tungsten” (consult your camera manual for more details) and take the pictures.

White Balance: Auto White Balance: Tungsten

(Tungsten icon highlighted in red)

Upside down method

If you do not have an ideal-light you can place a small piece of clear plastic, glass or cling wrap over the top of the ideal-scope and place the stone in the centre. Use ambient light, or hold a sheet of copy paper over the top to diffuse the light.

Using Pro-Consumer Camera

The simplest method is to use an Ideal-light and simply rest the camera on top of the ideal-scope.

If you do not have an ideal-light then you can use the ‘upside down'' method described above. But because the lens is usually larger the scope might not sit in place – so you may have to gently stick it on with some re-usable adhesive (3M Sticky Tac or Blu Tack, see photo below). Place a small piece of clear plastic, glass or cling wrap over the top of the ideal-scope and put the stone in the centre. Use ambient light, or hold a sheet of copy paper over the top to diffuse the light. If you have a flip out LCD screen use it, and you may choose to use manual focus.

Photographing Set Diamonds

You can hold a ring or ear rings with tweezers and balance them on the Ideal-light, pendants and brooches can just sit on it. Be sure the camera''s white balance is set to “Tungsten”. Stick the scope to the camera''s lens with re-usable adhesive, or hold the lens and camera together. Try to get plenty of light coming from behind the diamonds.

Expert vs Beginner Scope

Expert Scope Image Beginner Scope Image

Note: the beginner works well, but the expert model has more magnification and sharper features.

Battery Power

Fresh Batteries Weak Batteries

You get better definition, depth of field and picture quality with strong batteries in the Ideal Light.

Lighting Control

Blown out reflections Unwanted lights blocked

Unwanted light from windows or other sources can cause blown out highlights. Closing the blinds or turning off the unwanted light source such as table lamps can solve the problem. But you still some need overhead lights to take the pictures.

This is not a problem if you use the Ideal-Light. With the ‘Upside Down'' method you can hold a sheet of copy paper above the stone and block direct light sources.

A complete high speed professional photographic system, including auto cropping software and realistic diamond photo''s, go to www.ideal-scope.com/manuf_iscapture.asp

 

[jaz464]

I got my diamond from USA Certed. Martin was not able to view the diamond in person to describe it to me, but he did send it to an independent appraiser in my area so I could see for myself. After seeing the diamond myself I decided I did want to purchase it. You may want to consider this yourself.

 

[GeoAtl]

Thank you all very much for your opinions and your comments. They are all VERY MUCH APPRECIATED!

I am in no position to comment on the vendors' respective business models. I suppose I cannot reasonably expect the receive the great prices I have been quoted without making a few sacrifices -- the question is, which sacrifices are reasonable and which ones do you feel I should not be making? For instance, I absolutely refuse to consider EGL stones, regardless of the price, so that is simply not an acceptable sacrifice. Is it reasonable, however, to simply rely on the AGS 0 or GIA "excellent" certs in return for "drop shipment" and a price that is at least $1,000 lower than that I can get at WF, GOG, etc... This is not intended as a slight to WF, GOG or any other retailer -- they seem to provide terrific service and offer more information about their diamonds that what I can get with my virtual stones. Their business model is more expensive and the costs have to be passed on, of course. In the end, I have to decide, with the help of all of you at PS, which model fits my criteria the best.

No matter which diamond I choose, I will absolutely get it independently appraised. The question remains, however, what considerations beyond the ones that have been provided to me and that I have in turn outlined above are considered essential before the decision is made?

 

[aljdewey]

Date: 4/10/2006 4:41:23 PM
Author: GeoAtl
Here is one of the reasons I''m so confused: the poster in this thread (https://www.pricescope.com/community/threads/could-this-be-the-one.42739/ was not encouraged to obtain any additional tests/information on her significantly more expensive diamond, so I am just very confused about the difference in recommendations. Can anybody shed some light on this, please?

1. The poster in that thread was buying a VS1 stone, so there is less worry that a stone is eyeclean. It''s more important to check that with SI stones; some are eyeclean, some are not.

2. The poster in that thread selected an AGS0 stone with a recent DQD.....which means the stone passed light performance testing already. Your stones don''t specify that.

For you stones, the AGS stone is an SI2 and needs to be verified as eyeclean. Your only other option is the GIA stone, and it''s widely thought that GIA''s current cut grading system is much broader. Meaning that it''s tough to know if the cut is really a good one without doing an IS photo or some other verifier.

 

[aljdewey]

Date: 4/10/2006 5:48:33 PM
Author: GeoAtl
Thank you all very much for your opinions and your comments. They are all VERY MUCH APPRECIATED!

I am in no position to comment on the vendors'' respective business models. I suppose I cannot reasonably expect the receive the great prices I have been quoted without making a few sacrifices -- the question is, which sacrifices are reasonable and which ones do you feel I should not be making? For instance, I absolutely refuse to consider EGL stones, regardless of the price, so that is simply not an acceptable sacrifice. Is it reasonable, however, to simply rely on the AGS 0 or GIA ''excellent'' certs in return for ''drop shipment'' and a price that is at least $1,000 lower than that I can get at WF, GOG, etc... This is not intended as a slight to WF, GOG or any other retailer -- they seem to provide terrific service and offer more information about their diamonds that what I can get with my virtual stones. Their business model is more expensive and the costs have to be passed on, of course. In the end, I have to decide, with the help of all of you at PS, which model fits my criteria the best.

No matter which diamond I choose, I will absolutely get it independently appraised. The question remains, however, what considerations beyond the ones that have been provided to me and that I have in turn outlined above are considered essential before the decision is made?

Geo, if you are going to get it appraised, then I wouldn''t worry much up front. Most of the time, folks want more info up front to minimize the chances of having to reject and return ship stones to vendors. Hence the recommendations for more information.

As long as you pick an appraiser who can give you ALL the stats (Rich Sherwood, Dave Atlas, etc.) and evaluate light return, then you''ll be fine.

The most important thing: negotiate a really generous return policy that allows you to return for a full refund within a decent time frame, and contact your selected appraiser in advance to make sure he can evaluate your stone within that window of time.

I''d have a discussion with your vendor about what happens if you select the SI2 stone and it''s not eye-clean to YOU. In that instance, you shouldn''t have to pay for return shipping charges (because it''s being represented to you as eyeclean.)

Otherwise, I''d likely start with the GIA stone and have it appraised......the SI1 may stand a better chance of being eyeclean.

 

[Houseparty]

Date: 4/10/2006 5:48:33 PM
Author: GeoAtl
Thank you all very much for your opinions and your comments. They are all VERY MUCH APPRECIATED!

I am in no position to comment on the vendors'' respective business models. I suppose I cannot reasonably expect the receive the great prices I have been quoted without making a few sacrifices -- the question is, which sacrifices are reasonable and which ones do you feel I should not be making? For instance, I absolutely refuse to consider EGL stones, regardless of the price, so that is simply not an acceptable sacrifice. Is it reasonable, however, to simply rely on the AGS 0 or GIA ''excellent'' certs in return for ''drop shipment'' and a price that is at least $1,000 lower than that I can get at WF, GOG, etc... This is not intended as a slight to WF, GOG or any other retailer -- they seem to provide terrific service and offer more information about their diamonds that what I can get with my virtual stones. Their business model is more expensive and the costs have to be passed on, of course. In the end, I have to decide, with the help of all of you at PS, which model fits my criteria the best.

No matter which diamond I choose, I will absolutely get it independently appraised. The question remains, however, what considerations beyond the ones that have been provided to me and that I have in turn outlined above are considered essential before the decision is made?

Hi,
You seem like a pretty smart guy, and it sounds like you got things pretty well figured out. Like jasmine, I too purchased my stone from from Martin at USACerta and got a very well cut stone at a terrific price.

Like others said, AGS 0 is usually a subset of GIA Ex, so often the AGS0 is preferred. However, in your specific situation, #2 (the GIA) stone looks closer to a super ideal and has a better spread and thus, would be my choice. As someone else said, the market value of the clarity color combinations of these two choices are the same. But, sight unseen, buying a Si1 makes me a little more comfortable.

I think we are cut out of the same cloth.

You want the most impressive diamond, with no negatives, at the best value! Last month, I bought virtually the same stone from Martin as the GIA you are considering. Ask him if he sold a similar stone to "David" a month ago, and he should get a chuckle... This is what I bought, sound familiar?
Si1, I, 1.24, 60.9 D, 56 T, 41.0PA, 34.0CA, VG P and S, no fluor
(they are a essentially a pair).

Don''t wait too long, great stones at great prices sell quickly. OR my second choice stone at Blue Nile, has not sold yet, but they raised the price $558.

Let us know what you do.

Sincerely,
David

 

[GeoAtl]

aljdeway, please note:

1) the wholesaler has stated that both stones are eye-clean. Under the circumstances, I don''t see any difference between being forced to rely on the wholesaler or the retailer; and

2) the stone I am considering is also a 2006 AGS 0 stone with light performance rankings.

In light of the above, what additional information do you think is essential before the final decision is made?

 

[GeoAtl]

David, it seems like you and I are/were interested in essentially the same stones, so I actually used your stone's stats and the price from the previous thread as a guide for myself. The GIA stone that I am looking at here would probably end up being priced within +/- $50 of your price.

What I am still trying to figure out here is whether an AGS 0 certification or a "better" HCA score is a better predictor of the stone's performance. Along the same lines, the AGS 0 stone that I am considering is a few hundred dollars more expensive than a GIA stone with a higher HCA score -- why is that?

 

[jaz464]

Perhaps have them both sent to an appraiser so you can choose for yourself.

 

[jasontb]

Date: 4/10/2006 8:13:39 PM
Author: GeoAtl
which stone would you go with and why?

If I were you (no more info on stone availabel), I'd go with the AGS just because they grade light performance and have a tighter range of proportions that are considered ideal. But I'd rather buy from another retailer who could bring the stones in a give you more data on them.

 

[Rhino]

Hi Geo,

Just caught your post here. Since this GIA stone has the new GIA Report you also have lower girdle and star info. If you can get me that data I can create a fairly accurate Gem Advisor file for you giving you an idea to appearance and can also comment regarding brightness, fire and scintillation. Much more accurate than we could the AGS stone (since it doesn't contain any minor facet info).

Of course, as folks have stated, having a pro see it before the purchase is the best idea but without seeing it, having this additional data would help at least.

Kind regards,

 

[valeria101]

Between independent tools (HCA, IS) and what the labs give... how many cut grading details are there? And no two agree completely. ''Guess everyone has a personal set of such details they understand and trust: be it GIA''s, AGS''s, HCA etc. At least, that''s how this (and many others) threads sound like.

So... no wonder that price, HCA and lab grades don''t tally or folks'' opinions about them!



Still sticking with the GIA & SI1 though. As far as I know, the HCA tallies with IS - seeing the diamond is better than averaged numbers, of course. About those minor facets - GIA doesn''t allow extremes: slightly different looks are possible, but IMO ''slightly'' is the word unless you are looking at 40X magnification and Ideal Scope pictures blown up to the size of a dish. Sure I could tell extremes apart, but... between them is matter of preference rather than quality, again IMO.

Sure I''d like to try''em out as Diam Calc models as Jonathan says! (have the software too, although obiously the folks at Good Old Gold know to make better use of it

). The internal symmetry or lack thereof cannot be captured by the numbers on the lab report though - and this is why I avoid posting such models / while informative, they do not show what the diamond looks like in person. There could be a strong match if internal symmetry is real'' good, however the high finish grades (esp. the ''symmetry'' grade which is a different concept: see LINK) are a start but not quite the same.

 

[Garry H (Cut Nut)]

Date: 4/10/2006 9:06:03 PM
Author: Rhino
Hi Geo,

Just caught your post here. Since this GIA stone has the new GIA Report you also have lower girdle and star info. If you can get me that data I can create a fairly accurate Gem Advisor file for you giving you an idea to appearance and can also comment regarding brightness, fire and scintillation. Much more accurate than we could the AGS stone (since it doesn't contain any minor facet info).

Of course, as folks have stated, having a pro see it before the purchase is the best idea but without seeing it, having this additional data would help at least.

Kind regards,

Jonathon / Rhino I think this is a meaningless exercise because of the GIA rounding based on its GIA report data:

For example - if this was the proportions of a diamond - 57.5% table, 35.25 crown angle, 40.9 pavilion angle, 57.5% star and 82.5% lower girdle..........

 

[Garry H (Cut Nut)]

GEO you are very safe with the GIA proportions - it is most unlikly that it would look bad - but the idea that you can model an accurate image from data that is rounded is not going to help you.
For instance the data I listed:

57.5% table, 35.25 crown angle, 40.9 pavilion angle, 57.5% star and 82.5% lower girdle?

GIA can round this to 57% or 58%, 35 or 35.5, 40.8 or 41, 60 or 55%, and 80 or 85%.
The stone on the left is modeled with the smaller of each #, and on the right uses the larger #''s.
There is a big difference in their respective ideal-scope images, and their performance and spread.

 

[valeria101]

Not sure if this was meant as 'homework'... However, feedback can't hurt! Please ignore if annoying...
This is what I've been doing to GIA numbers all along, for better or worse.

Date: 4/11/2006 5:41:59 AM
Author: Garry H (Cut Nut)

Jonathon / Rhino I think this is a meaningless exercise because of the GIA rounding based on its GIA report data:

For example - if this was the proportions of a diamond - 57.5% table, 35.25 crown angle, 40.9 pavilion angle, 57.5% star and 82.5% lower girdle..........

Is this bad (or just terribly tedious) ?

table: 57.7
Rounding procedure: Table size is rounded to the nearest multiple of 1%
Interval of probable actual value: 57.66 - 57.7 -57.75

crown angle: 35.25
Rounding procedure: Crown angle is rounded to the nearest multiple of 0.5°
Interval of probable actual value: 34.75 - 35.25 - 35.75


pavilion angle: 40.9
Rounding procedure: Pavilion angle is rounded to the nearest multiple of 0.2°. Pavilion angles ending in odd numbers are
always rounded UP, for example 40.7° would be rounded to 40.8°
Interval of probable actual value: 40.8 - 40.9 - 41 (40.9 not a multiple of 0.2. Typo?)


star: 57.5
Rounding procedure: Star length is rounded to the nearest multiple of 5%
Interval of probable actual value: 55 - 57.5 - 60 (57.5 not a multiple of 5. Typo?)


lgf: 82.5
Rounding procedure: Lower-half (lower-girdle facet) length is rounded to the nearest multiple of 5%
Interval of probable actual value: 80 - 82.5 - 85 (57.5 not a multiple of 5. Typo?)


Wonder why the firmat does not tally... Are these numbers from a GIA report?


The rounding rules were taken from the webpage of GIA's facetware (LINK).

Now, assuming HCA was not made to account for this sort of rounding, but was meant to work with averaged proportions as usually available, it sounds like fair game to plot the resulting interval on the HCA chart and see if any patch of it falls out of grace. Like this: