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Differences Between a 41.1 Degree and a 41 Degree Pavilion Angle?

Dinky89484

Rough_Rock
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Sep 6, 2019
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I am looking at the specs of a round diamond with a 34.6 degree crown angle and a 41.1 degree pavilion angle. Combing through the zillion pages of threads on "ideal" pavilion angle and "ideal" crown/pavilion ratio, it seems that 41 is the absolute limit you would want the pavilion angle to be (the whole light falling edge thing). A 41.1 degree pavilion angle then...is bad or maybe just a little off of ideal? Thoughts?
 

lovedogs

Super_Ideal_Rock
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Joined
Jul 31, 2014
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18,014
I am looking at the specs of a round diamond with a 34.6 degree crown angle and a 41.1 degree pavilion angle. Combing through the zillion pages of threads on "ideal" pavilion angle and "ideal" crown/pavilion ratio, it seems that 41 is the absolute limit you would want the pavilion angle to be (the whole light falling edge thing). A 41.1 degree pavilion angle then...is bad or maybe just a little off of ideal? Thoughts?
41 is already too high (it's the absolute highest anyone would recommend, we usually say 40.6-40.8). I wouldn't go to 41.1
 

Dinky89484

Rough_Rock
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Sep 6, 2019
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How much leeway should I expect in terms of rounding? Could the 41.1 degree pavilion angle be closer to a 41 degree?
 

flyingpig

Ideal_Rock
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Say you find a diamond with 34.6 CA and 40.7 PA. 40.7 PA is the average of 8 individual pavilion angles. Of course, there will be deviation. Some will be 40.6 while other will be 40.9.
34.6 CA works well with PA of 40.5~40.9 (even 41.0). Therefore, this is a safe bet.
However, 41.1PA means some angles will be 41.2 or even 41.3. 41.3PA does not work well with 34.6CA and you will have leakage and wonkyness in that area. In addition, 34.6CA is also the average of 8 individual crown angles.
For this reason, even a diamond with 35.0 CA and 40.8 PA can have light leakage, because some individual pavilion angles can be 41.0 or higher.
It is possible that 34.6 CA and 41.1 can work if the acutual PA is lower than 41.1 and it is perfectly cut. However, that would be very unlikely.
In addition, when PA reaches 41.1, the table reflection gets larger, which most people find undesirable.

Between 40.9 PA and 41.1 PA, every 0.1 degree counts and diamond's appearance changes alot.
 

Dinky89484

Rough_Rock
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Sep 6, 2019
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Say you find a diamond with 34.6 CA and 40.7 PA. 40.7 PA is the average of 8 individual pavilion angles. Of course, there will be deviation. Some will be 40.6 while other will be 40.9.
34.6 CA works well with PA of 40.5~40.9 (even 41.0). Therefore, this is a safe bet.
However, 41.1PA means some angles will be 41.2 or even 41.3. 41.3PA does not work well with 34.6CA and you will have leakage and wonkyness in that area. In addition, 34.6CA is also the average of 8 individual crown angles.
For this reason, even a diamond with 35.0 CA and 40.8 PA can have light leakage, because some individual pavilion angles can be 41.0 or higher.
It is possible that 34.6 CA and 41.1 can work if the acutual PA is lower than 41.1 and it is perfectly cut. However, that would be very unlikely.
In addition, when PA reaches 41.1, the table reflection gets larger, which most people find undesirable.

Between 40.9 PA and 41.1 PA, every 0.1 degree counts and diamond's appearance changes alot.

Thank you guys! This helped me sift out a diamond that I was very eager to look at in person. All the specs were very ideal EXCEPT for the 41.1 PA.

Instead, I am going to be making an appointment to view a diamond with 56.5% Table Size, 61.1% Depth, 34.5 CA and 40.9 PA. These specs give me a much happier feel. Plus it scored a 1.4 on the HCA scale.
 

flyingpig

Ideal_Rock
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Thank you guys! This helped me sift out a diamond that I was very eager to look at in person. All the specs were very ideal EXCEPT for the 41.1 PA.

Instead, I am going to be making an appointment to view a diamond with 56.5% Table Size, 61.1% Depth, 34.5 CA and 40.9 PA. These specs give me a much happier feel. Plus it scored a 1.4 on the HCA scale.
I would like to add that GIA rounds CA to the nearest 0.5 and PA to the nearest 0.2.
This means you stone may not be GIA graded, unless those numbers are measured by tue vendor. We recommend diamonds graded by GIA or AGS.
 

Dinky89484

Rough_Rock
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Sep 6, 2019
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I would like to add that GIA rounds CA to the nearest 0.5 and PA to the nearest 0.2.
This means you stone may not be GIA graded, unless those numbers are measured by tue vendor. We recommend diamonds graded by GIA or AGS.
Yes! You are right! This is off of IGI. I'm looking at lab made diamonds and IGI is the best they've got for those. I know IGI should not be compared to GIA or AGS but unfortunately it's all I have to go by until I see it in person.
 

lovedogs

Super_Ideal_Rock
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Yes! You are right! This is off of IGI. I'm looking at lab made diamonds and IGI is the best they've got for those. I know IGI should not be compared to GIA or AGS but unfortunately it's all I have to go by until I see it in person.
For lab stones, IGI is ok, since there aren't tons of choices for certifications. But for specific questions about lab stones, post in the man made diamond forum, since we aren't allowed to explicitly discuss them here.
 

Karl_K

Super_Ideal_Rock
Trade
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Aug 4, 2008
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14,627
That combo could be fine, its the lgf% and what is in the averages that would make a difference. Scope images is/Aset would answer the question.

Edit: See flyingpig's post above.
 
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