Questions from a beginner - Pavilion angle / depth

[Katya DXB]

ASET is so badly taken it is useless.
I third the call for posting the numbers.

Could you please elaborate on why is it badly taken? Thanks

 

[idonotmatch]

Would love additional feedback on the following stones if possible:

https://www.yadavjewelry.com/products/Round-diamond-E-VVS2-YD2526140
https://www.yadavjewelry.com/diamonds/2726135

Thanks!

 

[Karl_K]

Could you please elaborate on why is it badly taken? Thanks

Light leakage into the top of the scope, stone tilted slightly, the back light is over bright and the placement of the stone vertically in the scope is off. Camera/stone/scope alignment also looks off.
It also does not closely match the numbers even taking into account the gia rounding.

 

[blueMA]

Would love additional feedback on the following stones if possible:

https://www.yadavjewelry.com/products/Round-diamond-E-VVS2-YD2526140
https://www.yadavjewelry.com/diamonds/2726135

Thanks!

Not a huge fan of either but prefer the second one.

 

[idonotmatch]

Not a huge fan of either but prefer the second one.

Based on the Price:Value ratio, or the cut of the stone?

 

[blueMA]

Based on the Price:Value ratio, or the cut of the stone?

I tend to concentrate on the cut when asked for a choice between select stones.

 

[idonotmatch]

Doubling down on the Canada Mark diamond - leaving JA as the best source. I've narrowed it down to the following list - any recommendations on best stones from the list?

https://www.jamesallen.com/loose-di...20600&ViewsOptions=Images&CM=True&Shape=round

Thanks in advance!

 

[blueMA]

Of those, this one
https://www.jamesallen.com/loose-di...f-color-vs2-clarity-excellent-cut-sku-5106131

 

[OoohShiny]

Doubling down on the Canada Mark diamond - leaving JA as the best source. I've narrowed it down to the following list - any recommendations on best stones from the list?

https://www.jamesallen.com/loose-di...20600&ViewsOptions=Images&CM=True&Shape=round

Thanks in advance!

Of those, I would say (IMVHO) that these are the best cut:

https://www.jamesallen.com/loose-di...f-color-vs2-clarity-excellent-cut-sku-5106131
Lower price than the rest, if you're happy with the inclusion then should be a good buy. (Looks like it's visible in the pavilion facets from some angles?)

https://www.jamesallen.com/loose-di...f-color-vs2-clarity-excellent-cut-sku-4632374
High crown, bigger, I can't see the inclusions - my preferred personal choice.

https://www.jamesallen.com/loose-di...-color-vvs2-clarity-excellent-cut-sku-5099848
High crown, inclusions will be invisible - I like VVS but you can buy the extra 0.21 carat of the one above with the same (invisible) visibility of inclusions for the same price as this.

The 1.71 seems like the winner to me.

What budget do you want to stick to?

 

[idonotmatch]

Thank you both. Budget is $20K. Any other recommendations on CanadaMark diamonds that I may have missed, would be more than welcomed

 

[John P]

See attached. Assuming angles are 100% accurate then yes...ideal. However, we know that GIA uses averages and rounding. The box I drew is probably more realistic. With the angles, it has the potential to be excellent to ideal cut.

@sledge and @blueMA , it may be useful to know that this chart doesn't correspond to AGSL guidelines for Ideal/0 in their Platinum light performance metric. It reflects the more lenient ID-EX-VG system used in their 2D "Gold" proportions system from 2008.

Gold (2D) Proportions Quality Report example here.
http://www.americangemsociety.org/page/agslabsgolddiamon

That report was designed to mimic GIA's more factory-friendly approach, giving a predictive grade based on averaged 2D proportions. Those charts are not as liberal as GIA's proportions system, but they are not as strict as the cutting guides for the 3D light performance grade.

Here's prior discussion on the topic, with examples of changes over the years.
https://www.pricescope.com/communit...tes-can-experts-chime-in.129850/#post-2285615

 

[sledge]

Thank you @John Pollard. I wasn’t aware I was using antiquated data. I will read the linked thread and am hopeful a different reference is available that is as quick and easy but I suspect not.

 

[blueMA]

@sledge and @blueMA , it may be useful to know that this chart doesn't correspond to AGSL guidelines for Ideal/0 in their Platinum light performance metric. It reflects the more lenient ID-EX-VG system used in their 2D "Gold" proportions system from 2008.

Gold (2D) Proportions Quality Report example here.
http://www.americangemsociety.org/page/agslabsgolddiamon

That report was designed to mimic GIA's more factory-friendly approach, giving a predictive grade based on averaged 2D proportions. Those charts are not as liberal as GIA's proportions system, but they are not as strict as the cutting guides for the 3D light performance grade.

Here's prior discussion on the topic, with examples of changes over the years.
https://www.pricescope.com/communit...tes-can-experts-chime-in.129850/#post-2285615

Thanks @John Pollard - of course the chart is just a reference as is the HCA and other tools.

 

[blueMA]

Thank you @John Pollard. I wasn’t aware I was using antiquated data. I will read the linked thread and am hopeful a different reference is available that is as quick and easy but I suspect not.

Sledge - the chart is still useful to get a sense good proportions, and while it's not absolute it's not exactly antiquated. This is why you still have to look at the stone images/videos.

If you make an excel chart out of all super-ideal vendor inventories, you'll notice that the majority fall near the middle of the ideals plot, and most drop-shippers tend to carry the edge of the ideals (brand-rejects).

 

[John P]

Thank you @John Pollard. I wasn’t aware I was using antiquated data. I will read the linked thread and am hopeful a different reference is available that is as quick and easy but I suspect not.

@sledge, you're very welcome. And to be clear, it's not antiquated. That Gold report is still offered as a less-strict path for producers who focus only on 2D averages.

This causes some confusion because, according to those charts, a producer can in send a diamond and will reliably receive AGS Ideal or Excellent based only on the diamond's 2D average proportions.

However the same diamond could fare differently in the 3D Platinum metric, where a full 3D scan is made and ray-traced specifically. Not only are there stricter proportions requirements, details of minor facets, brillianteering, optical precision and variance from average come into play in that assessment.

So you have this Gold "Ideal" (the chart that was posted) but the more commonly discussed Platinum "Ideal/0" is a far stricter target.

...hopeful a different reference is available that is as quick and easy but I suspect not.

There are no hard charts because the 3D platinum metric is diamond-specific. Diamonds with identical average proportions can receive different performance grades based on how the 57 facets work together, beyond the numbers.

AGSL does provide cutting guidelines to manufacturers - I'll use one in my next post - but they are stipulated as guides only. The final light performance grade for a given diamond is only derived after assessing that specific diamond.

 

[sledge]

Sledge - the chart is still useful to get a sense good proportions, and while it's not absolute it's not exactly antiquated. This is why you still have to look at the stone images/videos.

If you make an excel chart out of all super-ideal vendor inventories, you'll notice that the majority fall near the middle of the ideals plot, and most drop-shippers tend to carry the edge of the ideals (brand-rejects).

Very true. I responded while on my mobile. I had more written that basically said the same as you -- "it may not be an exact tell tale, but it gets us close". When I normally look at those and post them, I draw a bigger box going 1 spot over in every direction (actually yields 9 different cuts) to give a more realistic idea of how the stone COULD be cut. When all, or the bulk of those land in ideal territory then I start to feel pretty good about the stone. Not to say it will be a champ, but at least it has the POTENTIAL to be a super star.

So like you, I am using as an elimination tool and then using images and videos to make a final determination.

 

[blueMA]

There are no hard charts because the 3D platinum metric is diamond-specific. Diamonds with identical average proportions can receive different performance grades based on how the 57 facets work together, beyond the numbers.

@John Pollard Would you agree that if a diamond has good proportions, the image has very high optical symmetry, good equal star facet patterns along with Arrows patterns, with minimal table obstructions/clustering/leakage, the chances are that the 57 facets work well together?

 

[John P]

Here's an example of the 2D proportions system's departure from the 3D metric.

Diamond average measurements: 55T 34.7CA, 41.1PA

Gold report = AGS Ideal or Excellent, depending on how the scanner burps out averages that day.


Platinum report = quite variable, depending on minor facet choices, optical precision, brillianteering and other details. Depending on cutting intelligence and execution: AGS 1-4 in performance. No chance of Ideal performance, however.

Thanks @John Pollard - of course the chart is just a reference as is the HCA and other tools.

Sure, when used in proper context. In this case those Gold charts are not predicting AGS Ideal/0 in light performance. They show Ideal proportions in a lesser metric. That distinction may be useful to note.

 

[blueMA]

In this case those Gold charts are not predicting AGS Ideal/0 in light performance.

I tend to stay away from the edge of the ideals, and have heard many times @Wink and others mentioning many 3D scanned AGS0 stones not performing optimally compared to some superideals that I notice are usually in the sweet spots in comparison.

Out of curiosity, do any cutters still abide by those 2005 AGS cut recommendations? I see most vendors ranging near the T ideal proportions.

 

[John P]

@John Pollard Would you agree that if a diamond has good proportions, the image has very high optical symmetry, good equal star facet patterns along with Arrows patterns, with minimal table obstructions/clustering/leakage, the chances are that the 57 facets work well together?

Sure. Not in question. I posted because I thought it may be useful to mention that those charts accompany a different AGS system which doesn't employ light performance. I'm regularly clarifying this with pros who find them on the AGS site, because it's not made very evident on the charts themselves.

 

[OoohShiny]

Every day is a school day with John around!

Thank you very much for posting that info, it's really useful

 

[Karl_K]

Something to keep in mind that the platinum report 3d score and the cutting guidelines are two different thing.
There are many combinations that when cut with reasonable precision and with excellent optical symmetry that get ags0 that the cutting guidelines give 1 or higher.
With the 3d score as long as the computed results come out in the 0 range and its does not hit any of the disqualification criteria it gets ags0.
On the other hand just because the cutting guidelines say its ags0 does not mean its 3d ags0.
It does mean it has the potential to be 3d ags0.

 

[John P]

I hope the OP doesn’t mind a swerve to answer some good questions.

Out of curiosity, do any cutters still abide by those 2005 AGS cut recommendations?

Context first. AGS published 115 guides for RB organized by mm spread and table size. Those in the conventional ideal range follow the main cutter’s line rather closely, with the most robust areas system-wide landing on modern Tolkowsky. That’s no surprise. We and other niche specialists were glad to see scientific validation of practices we were following long before 2005. Some of us presumed it could change the industry.

But the answer is that few producers use them. Not just because demand for 0 is relatively small, but also due to what @Karl_K mentioned. << just because the cutting guidelines say its ags0 does not mean its 3d ags0. >>

Consider the logic. If you’re a major producer GIA, IGI and HRD serve up nice wide proportions targets and you know the cut grade before sending to the lab. Why would you ever aim for AGSL’s smaller 'science' target, polishing more weight away, and also uncertain of the final grade until their proprietary 3D ray-tracing is applied? …Thus the answer to your question brings us full circle. Producers rejected AGS’ scientific guides in 2005, in favor of ironclad charts from larger labs presenting easier targets. That's why AGSL introduced the Gold metric three years later, with a relaxed “2D ideal” target and predictable grades based on 2D average proportions. They had intended to push the industry forward. Instead, the industry pushed back.

Obviously there are producers who will target “AGS 3D ideal” proportions for customers willing to pay for it. Those customers include cut-conscious sellers serving cut-aware audiences like this one, along with AGS member jewelers, advocates and other cut nerds. But even in the AGS friendly USA, fewer than 2% of all diamonds get sent to AGSL - and many of those are submitted for reports that are less strict than their 3D platinum metric.

I see most vendors ranging near the T ideal proportions.

Correct. But internet vendors are just the tip of a massive iceberg. If you were a trader analyzing the totality of polished output from Mumbai to Antwerp to New York or (this would be cheaper) if you just get an office, a RapNet subscription and a pizza, and start pulling numbers on the >1,000,000 RBs for sale - you’ll see an overwhelming trend towards proportions the regulars here would call 'steep-deep.' Why? Simple economics. Steeper angles put more weight in diamonds. More weight brings more profit. That's why the majority of the world's RB output is > HCA 2.0 and has deficiencies in IS or ASET.

So I hope you don’t mind if I revisit this comment -

If you make an excel chart out of all super-ideal vendor inventories, you'll notice that the majority fall near the middle of the ideals plot, and most drop-shippers tend to carry the edge of the ideals (brand-rejects).

Super-ideal vendor inventories represent a comically tiny fraction of world output. Even adding the larger inventories classified as ‘signature’ or ‘ideal’ from big online sellers, you’re only scratching the tip of a steep-deep iceberg (see what I did there?). For that reason I applaud the sellers making an honest effort to cull and present options capable of serving cut-educated shoppers. And thus, I would not characterize the options at the 'edge of the ideals' as brand-rejects. I would call them promising hopefuls which finished above the average chaff.

 

[John P]

Every day is a school day with John around! Thank you very much for posting that info, it's really useful

Tip of the hat. And you're welcome.

 

[blueMA]

@John Pollard Thanks for the detailed response. I did mean H&A brand vendors when I was mentioned the vendors raging near the T-ideals, of course.

I noticed that the majority of "wholesale" drop-shippers rarely carry the exact optimal T proportions although they attempt to brand the stone as their top quality stones, and when I do find them more often than not there were something wrong with the stones. I read somewhere a while back that there are stone buyers (for various brands) who get the first grabs of best cut stones by suppliers, and the rest end up on online drop-shipper inventory? When I did find decent ones, they also soon end up getting grabbed by some of the more well known modified drop-shipper in-house inventories.

 

[Karl_K]

Some of the cutters that were cutting h&a quality stones found they were not getting enough of a premium for it and turned what they knew about control of the cutting process into creating wide ranging pavilion angled stones that at first glance appear to have good numbers and in other cases to push the border of gia ex even further down. The results is some of them having good looking numbers but poor looking IS/ASET with a lot of variation around the stone.
The planning software even has settings that allow them to plan it.

 

[blueMA]

Some of the cutters that were cutting h&a quality stones found they were not getting enough of a premium for it and turned what they knew about control of the cutting process into creating wide ranging pavilion angled stones that at first glance appear to have good numbers and in other cases to push the border of gia ex even further down. The results is some of them having good looking numbers but poor looking IS/ASET with a lot of variation around the stone.
The planning software even has settings that allow them to plan it.

I read this on PS a while back - Should I interpret that they're deliberately sabotaging the stock so that H&A gets more differentiated to justify for higher premium?

 

[Karl_K]

I read this on PS a while back - Should I interpret that they're deliberately sabotaging the stock so that H&A gets more differentiated to justify for higher premium?

No, they are not targeting h&a any longer. They are targeting higher weight retention but the numbers still look good on the report.

 

[blueMA]

No, they are not targeting h&a any longer. They are targeting higher weight retention but the numbers still look good on the report.

Ah OK thanks for that clarification. It's sad they'd deliberately twist the pavilions which directly compromise light performance while they're perfectly capable of producing high precision H&A stones. For economics or not, dark nevertheless...

 

[rockysalamander]

@idonotmatch

I'm not sure where you landed on color/clarity preference, but I encountered this diamond while searching for someone else. It has good (not perfect) return and over 2 carats and just above your top budget. So, if its too much, I totally understand, but thought it worth posting.
https://www.jamesallen.com/loose-di...color-vs1-clarity-true-hearts-cut-sku-4297772

This is on par, a little smaller. Also AGS Certified.
https://www.jamesallen.com/loose-di...color-vs2-clarity-true-hearts-cut-sku-3353504

The one posted by @oohshiny is higher color and a bit smaller and more expensive.
https://www.jamesallen.com/loose-di...-color-vs2-clarity-excellent-cut-sku-4632374c

Within this same price range, you can find super-ideals. This is a higher color, and eyeclean SI1.
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3988017.htm

or this H VS2
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3988016.htm