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Anatomy of diamonds, learning from the stones

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
Hi dear community

I have posted pictures of these two diamonds before and apologise if I come back again with more questions. New to the field and still learning.

So the two stones are very different compared to each other but are also both slightly different to common round brilliants. I have learned so far, that The pattern of the chunkier stone could result from shorter lower girdle facets. So I’m wondering what causes the pattern of the other stone? It produces long beams right out of the centre. Both are stones from older jewellery, however, I don’t know exactly how old.

Thank you for your thoughts!
 

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tyty333

Super_Ideal_Rock
Premium
Joined
Dec 17, 2008
Messages
21,659
Longer lower halves to answer your question. 80% will cause long, thin arrows.

Edit...here is a RB with 80% lower halves
 

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
Longer lower halves to answer your question. 80% will cause long, thin arrows.

Edit...here is a RB with 80% lower halves
Thank you! Yes, that is similar. What I’m missing in my stone and what I find strange, is the circle in the middle of the stone (before the arrows start). In your example it is well seen, in my stone, the arrows start in the center. Why would that be?


There is a similar one: it got 85%...
 
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Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
Or maybe in other words: what causes that inner circle around the culet, if viewed from the top, to be there or, as is with my stone, not to be there? Does that make sense?
 

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
So I tried to visualise it. One stone with the "inner circle", the other with no such circle. What would cause that phenomenon? Thank you so much for your time and help!

IMG_7268.jpeg IMG_7268.jpg IMG_7260.jpeg IMG_7260.jpg
 

Karl_K

Ideal_Rock
Trade
Joined
Aug 4, 2008
Messages
9,443
Differences in pavilion angle..goes away in steep pavilions.
Or more accuratly gets larger and blends in with the table edges.
 

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
Thank you Karl! So the stone with no “inner circle” just has a steep pavilion? Is that just a way to cut?
 

sledge

Ideal_Rock
Premium
Joined
Apr 23, 2018
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4,441
Below are proportions from the 2 carat stone at BN you posted.

Pavilion = 42.6

For a MRB, we recommend 40.6-40.9, maybe a 41 if paired with the proper crown. I point this out because what may "sound" like small variances (ie 41 vs 42.6) can make large impacts when talking diamonds.

This stone has a very steep pavilion.

Of course a 68 table, 36.5 crown, 63.5 depth, 60 stars with 85 LGF's and 6.5% girdle are also issues and contribute to good cut vs excellent from GIA.

By chance do you have certs on the stones you are asking about?

Screenshot_20200226-131952_Drive.jpg
 

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
No, I don’t. It
Below are proportions from the 2 carat stone at BN you posted.

Pavilion = 42.6

For a MRB, we recommend 40.6-40.9, maybe a 41 if paired with the proper crown. I point this out because what may "sound" like small variances (ie 41 vs 42.6) can make large impacts when talking diamonds.

This stone has a very steep pavilion.

Of course a 68 table, 36.5 crown, 63.5 depth, 60 stars with 85 LGF's and 6.5% girdle are also issues and contribute to good cut vs excellent from GIA.

By chance do you have certs on the stones you are asking about?

Screenshot_20200226-131952_Drive.jpg

No, unfortunately I don’t. The stone comes from an older ring. When I had it reset, the jeweller mentioned, that it’s cut was different to a common round brilliant. I did some research and thought maybe transitional or early round brilliant. But now I’m not so sure. It just seems to be cut differently. The old ring could have dated back to the 40ies or 50ies, maybe 60ies. The thing is, that it is quite proportional and sparkles so nicely and despite being different, I love it.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,170
The red arrow is the Table Reflection. In this stone it is about 80% of the width of the table (the wobbly blue arrow).
80% = 48% depth of pavilion relative to the diameter of the diamond.

The old cut diamond has about a 50% Table Reflection so has about a 45% pavilion depth.
You can google charts that show you the % to angle etc.
But essentially 100% refelction = 45 degrees and Ideal is 40.75 = 43%. Just under 40 degrees is close to 0% reflection.

1582839663441.png
 

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
Thank you
The red arrow is the Table Reflection. In this stone it is about 80% of the width of the table (the wobbly blue arrow).
80% = 48% depth of pavilion relative to the diameter of the diamond.

The old cut diamond has about a 50% Table Reflection so has about a 45% pavilion depth.
You can google charts that show you the % to angle etc.
But essentially 100% refelction = 45 degrees and Ideal is 40.75 = 43%. Just under 40 degrees is close to 0% reflection.

1582839663441.png
Thank you, Garry, for this expertise. So in terms of perfection, this stone is far from it, if I read correctly? Nevertheless, it is one of the nicer ones I’ve seen around in terms of brilliance and fire - or maybe I just think that because I love it dearly.

As for the old cut... to which one are you referring?
 

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
Thank you! I will look out for those. This is all new to me but so fascinating! So you think the bigger stone is indeed and old / older cut? I was unsure as it lacks a culet.
 

Roselina

Shiny_Rock
Joined
Feb 1, 2020
Messages
237
I dont know which is bigger - but the solitaire is a old european cut
Oh, I didn’t realise. The one in the first picture, yes. I always thought it looks quite different but lacking a culet I thought not much about it, perhaps early round brilliant or even recut at some point. It has less sparkle indeed and does look better in dim light.
 
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