Rare proportion combo? CA 35.1 & PA 40.8

[Double E]

In an attempt to learn more, I've noticed an inhouse stone of 1 of a famouse super ideal vendor here in PS with below spec., which what caught my attention most is the combo of CA 35.1 & PA 40.8. In contrast to what's frequently mentioned in the forum, which higher CA compliment with lower PA within ideal range & vise versa; the mentioned stone is to a certain extend in the steeper end for both CA & PA.

Table: 55.9
Depth: 62
CA: 35.1
PA: 40.8
Crown hieght: 15.6
Pavillion: 43.1
LGF: 77
Star: 50

My question is does that mean the said "complimentary" CA PA combo is in fact not a must for super ideal performance? And anybody could give further insight on what the particular personality & characteristc are on such kind of stones?

Look forward to hear from you all~

 

[kmoro]

In an attempt to learn more, I've noticed an inhouse stone of 1 of a famouse super ideal vendor here in PS with below spec., which what caught my attention most is the combo of CA 35.1 & PA 40.8. In contrast to what's frequently mentioned in the forum, which higher CA compliment with lower PA within ideal range & vise versa; the mentioned stone is to a certain extend in the steeper end for both CA & PA.

Table: 55.9
Depth: 62
CA: 35.1
PA: 40.8
Crown hieght: 15.6
Pavillion: 43.1
LGF: 77
Star: 50

My question is does that mean the said "complimentary" CA PA combo is in fact not a must for super ideal performance? And anybody could give further insight on what the particular personality & characteristc are on such kind of stones?

Look forward to hear from you all~

Just to clarify, is it listed as a super ideal or is it just from a super ideal vendor (not all of their inventory is super ideal) ... I would expect the CA/PA is extremely important ... sorry if this is a dumb question ...

 

[Double E]

Just to clarify, is it listed as a super ideal or is it just from a super ideal vendor (not all of their inventory is super ideal) ... I would expect the CA/PA is extremely important ... sorry if this is a dumb question ...

Yes it's from their super ideal line. Occationally in some other super ideal vendors, we can also see some stones of CA 34.8 & PA 40.9 or CA 34.9 & PA 40.8 or similar, which caused my curiosity already; and the one i mentioned in this thread is even more extreme with the CA is higher than 35. So, I quite understand you also wanted to know the tricks behind, as these are also important to me and other consumers.

 

[kmoro]

Thanks! I didn’t realize a vendor would go outside
of their own ideal spec’s for their ideal category ... but it would make sense that some “odd”’looking combos create ideal light performance - since there are many facets and angles, not just the ones we plug into HCA, for example .. and also explains the weakness in HCA ... it can’t take everything into account - still surprises me that these outliers would make ideal grade based on light performance alone L(although this is the desired end product) - I would assume these are exceptional then.
Now I’m going to be looking for these diamonds too! Feeding my obsession, lol.

 

[gm89uk]

Do you mean a crafted super ideal or true hearts by JA which selects already cut very nice stones? There is a difference

 

[flyingpig]

You really do not need to worry complimentary PA/CA when your pavilion angle is 40.6-40.9.
When your PA gets 41, now it gets interesting, and that's when we normally talk about complimentary angles.

CA 34.7~35.2 coupled with PA 40.8~40.9 is generally fine.

The stone you mentioned has 40.8 PA, which can work well even with 35.5 CA as long as it is precision cut.

 

[Double E]

Do you mean a crafted super ideal or true hearts by JA which selects already cut very nice stones? There is a difference

Not JA, it's from one of the famous vendors. e.g. CBI, WF, BGD.

You really do not need to worry complimentary PA/CA when your pavilion angle is 40.6-40.9.
When your PA gets 41, now it gets interesting, and that's when we normally talk about complimentary angles.

CA 34.7~35.2 coupled with PA 40.8~40.9 is generally fine.

The stone you mentioned has 40.8 PA, which can work well even with 35.5 CA as long as it is precision cut.

That sounds nice, we get more flexibilities when selecting stones. Will this give more intense fire? May be we are over simplifying such question / thought, as ideal cutters are at a higher level than us who are talking about only the numbers.

But 1 thing I've learnt while looking for the stone for my lady, is it's harder to get the ideal cut precision for steep CA and PA because the space between the hearts and Vs will become slimmer. So if a stone with high CA and PA which classified as super ideal (assuming there may still be precision variances within these top line stones) you could be pretty sure it is of the highest precision. Comments welcomed~

 

[jp201845]

It scores a 1.8 on the HCA but only very good on Scintillation.

 

[yssie]

Whoa. Okay. Lots of misconceptions and misunderstandings here.

1. All labs average (mean, not median) and round the numbers on the report - some round some proportions more than others. This means that the single-value proportions listed on the report are not representative of real-world variance around the stone.

2. The scanners that the labs use are only accurate to 0.1-0.2 degrees angular. Take a look at Sarine’s (for example) product list:
https://sarine.com/

3. This sounds like an AGS report, and the vendors you name send their signature stones out for Diamond Quality Documents with Light Performance. AGS DQD does not use a strictly proportions-based grading methodology like the GIA (or some of the other AGS reporting styles) - “Light Performance” involves scanning the diamond and computing light return, and final cut grade is based on determination of “quality” and “quantity” of computed light return. See below for info on AGSL reports and LP grading:
https://www.americangemsociety.org/page/documentarchives
http://www.agslab.com/spie/spie_lo_res.pdf

4. I don’t know where anyone’s getting the idea that numbers - any numbers for any brand - are inviolable requirements. WF’s site explicitly states that In rare cases, it is possible for an A CUT ABOVE® to exceed one or more of these specifications, but only if the light performance analytics are superb:
https://www.whiteflash.com/a-cut-above-diamonds-specifications-and-qualifications/

I’m on my phone and can’t do a thorough search for similar documentation from BGD and CBI, but if that documentation exists I guarantee that it will include verbiage to similar effect - for very good reason.

5.

But 1 thing I've learnt while looking for the stone for my lady, is it's harder to get the ideal cut precision for steep CA and PA because the space between the hearts and Vs will become slimmer. So if a stone with high CA and PA which classified as super ideal (assuming there may still be precision variances within these top line stones) you could be pretty sure it is of the highest precision. Comments welcomed~

The agslab paper I linked earlier will clear up a lot of confusion... but in short: no truth whatsoever to this assertion.

Optical precision is optical precision, end of story. Even if certain nuances of proportions combinations made achieving optical precision harder (which isn’t the case)... the result of difficulty of accomplishment would not be greater optical precision.

All facets, major and minor, play into the optical pattern that you see through a H&A viewer. Table, pavilion mains, and lower halves are certainly critical contributors. Different vendors may hold their diamonds to different standards of symmetry, but those standards are enforced uniformly across all proportions combinations.

 

[flyingpig]

BGD signature is more flexible with CA than WF ACA and CBI are.

 

[Lula]

This thread from 2015 may be helpful.
https://www.pricescope.com/communit...on-combo-ca-35-1-pa-40-8.245473/#post-4461291