Fire difference between BGD stones

[sledge]

Yup, A gent's 3 stone ring!

I think I'm an 11.5, so I might have the sausages to pull off a triple 1 carat stones. My girl may not like me having more bling than her though.

 

[Wewechew]

Thank you for sharing the additional information @Wewechew. Before we get too much further, both are gorgeous stones and I am glad you got the opportunity to see both close up.

I didn't start studying diamonds until a few months back, so I feel my resources and ability to explain what I am thinking is fairly limited. I will do the best I can with my limited knowledge. In short everything works together (CA, PA, table, depths, star facets & LGF's). While many factors are very close, you are starting to see minor changes in multiple areas that are combining to create one stone that you found visually appealing and the other you didn't.

Here is what I have noticed:

• Crown angle = 34.7 both
• Crown thickness = 15.3 WF | 15.7 BGD
• Table = 55.8 WF | 54.6 BGD

With the WF table being larger and the CA remaining the same the crown thickness is forced to change to a lower value. However, this slightly changes the facets as well.

This led me down a rabbit hole where I started building simplistic 2D models in my CAD program. Below are some screen captures which led me to some more points I found interesting.

• BGD stone measures 5.42 x 5.44 x 3.36. Additionally the cert indicates a depth of 61.9%. Having a non-perfect round, I checked both measurements:
  • 3.36 / 5.42 = 0.619926199, or 62.0% rounded appropriately
  • 3.36 / 5.44 = 0.617647059, or 61.8%
  • 3.36 / 5.43 (avg) = 0.61878453, or 61.9% - Okay, seems reasonable
• WF stone measures 4.77 x 4.79 x 2.96. Depth is reported at 61.8%. Again, more math:
  • 2.96 / 4.78 (avg, having learned the lesson already) = 0.619246862, or 62.0%
  • 2.96 / 4.77 = 0.620545073, or 62.1% (makes sense, divide same # by smaller #)
  • 2.96 / 4.79 = 0.617954071, or 61.8%
• Seems I'd use the average, high or low value on both stones instead of the average on BGD and high on WF. Of course, AGS probably measured with a Sarin machine and rounded that value as well.
• In a theoretical world, neither model produced an EXACT cutlet point using the size, depth % and angles reported. However, WF was closer.
• What I found interesting is that the 40.76 degree angle I discovered is the EXACT angle where the cutlet shown on the ASET turns red or green. Neither is necessarily better or worse, just a matter of how the light refracts back at a certain color because of a small change in angle. If you look at the actual WF ASET image, you will see where most of it is green, but some is red.
• Oddly enough, the exact angle to form a cutlet on the BGD stone was 40.7 (despite reported pavilion of 40.9) which falls below the 40.76 division line and makes the cutlet appear green in the ASET.
• My model is glorified chicken scratch in comparison to the tools WF & BGD have, so I am not trying to make any final conclusions. I just noted these as oddities and points of interest to me.

https://www.whiteflash.com/about-di...n/aset---table-reflection-whiteflash-1420.htm





Moving on.

• LGF's = 76 WF | 78 BGD
• Star Facets = 53 WF | 52 BGD

Differences between the LGF's seem minor but many people tend to favor "fat arrows" which come from 75-76 LGF's. Looking at still photos, you can see the arrow difference between the two stones. WF actually has a good write-up on this. The examples used in the beginning are more extreme (75/80/85) but towards the end they end up comparing closer facets (78/80/82).

In short, lower LGF's perform better with less lighting and larger LGF's perform better in brighter lighting environments. The differences are minimal and there are minor trade-off's with both. Other characteristics come into play but generally speaking a 75-80 LGF is "good".

https://www.whiteflash.com/about-diamonds/diamond-education/facets-the-lower-halves.htm

Based on all this I think the 76 LGF in combination with other minor factors made a difference in your viewing/preference of the two stones.

Also, here is some good information how star facets can play into the equation as well. Again, minor but really at this level we are about nitpicking anyhow, so I am going to throw it out there. I haven't personally compared star facets and won't comment much other than to say it seems to me very negligible with a 52/53 value.

https://www.prosumerdiamonds.com/star-facet/

Wow. Thank you for taking the time to do this. So now I know what to look for when I purchase a new diamond going forward

 

[OoohShiny]

You are making my brain hurt, @sledge LOL

Kudos for your research, though

You'll be the next @Karl_K at this rate

I can't remember if there's a free download of one of the wire-frame diamond design programs somewhere!

 

[Double E]

Thanks Sledge for giving us such detailed and informative response again! Here is always a good place when people loves to share~

By browsing the inventory of different ideal vendors (ofcox not every single stone though), it seems more common there's stones with40.8 PA and CA from 34-35, which for What I have been reading here in PS, is more complimentary combo; while at the same time there are noticeably less diamonds which are high in both CA and PA, e.g. 40.8 PA pairing with 34.9 CA.

However, these stones with high CA and PA seems contradictory to the said complimentary concept, despite still being offered by ideal cut vendors.

How is the performance difference? In terms of fire and brilliance? Could Sledge or other experts kindly try to look into it?

 

[Double E]

sledge, Dancing Fire, OoohShiny, diamondseeker2006 and any other experts, any idea on my confusion above? Appreciated for your help!

 

[MissGotRocks]

Sledge,
I think you are quite correct that for a buyer with a keen eye, there are 'taste' options even in the super-ideal realm, and even within individual brands of super-ideals.

And thank you for your nice comments!

I wholeheartedly agree with this!

 

[diamondseeker2006]

Thanks Sledge for giving us such detailed and informative response again! Here is always a good place when people loves to share~

By browsing the inventory of different ideal vendors (ofcox not every single stone though), it seems more common there's stones with40.8 PA and CA from 34-35, which for What I have been reading here in PS, is more complimentary combo; while at the same time there are noticeably less diamonds which are high in both CA and PA, e.g. 40.8 PA pairing with 34.9 CA.

However, these stones with high CA and PA seems contradictory to the said complimentary concept, despite still being offered by ideal cut vendors.

How is the performance difference? In terms of fire and brilliance? Could Sledge or other experts kindly try to look into it?

Right, a crown angle in the low 34 range can have the 40.9 pav angle. A crown angle closer to 35 will have a 40.6 pav angle, generally. Many like the 34.5, 40.8 combo.

I think there are two major factors when choosing a superideal diamond, and it's pretty simple. The lower girdle facets can be fat or skinny, and people have preferences on that. Also, table size is a factor...a 57-58 table might show slightly more brightness while a 54 table might show slightly more fire. But the thing is, diamond size has something to do with this as well. In a 1 ct stone, you may not be able to look at it and be able to accurately say whether the lower girdle facets are 76 or 78. It matters less the smaller the stones. But if I were choosing a 2 or 3 ct superideal, I am sure I'd favor 76-77 as I enjoy fatter facets with slightly broader light reflection. Remember, though, we are talking about very slight differences that the average person wouldn't even be able to tell. All superideals are brilliant or they wouldn't get the AGS 0 grade.

I think this conversation might be more useful if you show us stones you are interested in and we can tell your which we'd prefer and why. But as we have said many times, it's really hard to go wrong with any superideal cut stone from PS vendors because the specs are so narrow.

 

[Double E]

Right, a crown angle in the low 34 range can have the 40.9 pav angle. A crown angle closer to 35 will have a 40.6 pav angle, generally. Many like the 34.5, 40.8 combo.

I think there are two major factors when choosing a superideal diamond, and it's pretty simple. The lower girdle facets can be fat or skinny, and people have preferences on that. Also, table size is a factor...a 57-58 table might show slightly more brightness while a 54 table might show slightly more fire. But the thing is, diamond size has something to do with this as well. In a 1 ct stone, you may not be able to look at it and be able to accurately say whether the lower girdle facets are 76 or 78. It matters less the smaller the stones. But if I were choosing a 2 or 3 ct superideal, I am sure I'd favor 76-77 as I enjoy fatter facets with slightly broader light reflection. Remember, though, we are talking about very slight differences that the average person wouldn't even be able to tell. All superideals are brilliant or they wouldn't get the AGS 0 grade.

I think this conversation might be more useful if you show us stones you are interested in and we can tell your which we'd prefer and why. But as we have said many times, it's really hard to go wrong with any superideal cut stone from PS vendors because the specs are so narrow.

Thanks so much for your post! You may find more details for my stone in my other thread linked below with ASET and IS images for your interest

https://www.pricescope.com/community/threads/aset-and-is-image-evaluation.242975/

 

[diamondseeker2006]

Beautiful stone! I think there is a point where people can get into analysis paralysis. The superideals are at the top of the stack already. The differences are ever so slight.

 

[Dancing Fire]

Beautiful stone! I think there is a point where people can get into analysis paralysis. The superideals are at the top of the stack already. The differences are ever so slight.

Yep, We are nitpicking over 1.5 - 2% of MRBs on earth.

My own top ideal cut preferences are...
Table of 54-55.5%, crown height 15.5 - 15.7%, LGF 76 - 77%, crown angle 34.5 - 34.8. and Pavil angle 40.7 - 40.8