Crown & Pavilion angle to angle, Min-Max

[new4diamond]

What are the Minimum to Maximum variation in crown & pavilion angles in a diamond to consider it an Ideal/Excellent cut?

Say the AGS lab report states Ideal cut with a Crown 34.9 / Pavilion 40.9 both are averages. Can the angles vary .2 or .5 or maybe .9 from min to max and be an Ideal cut?

 

[MissGotRocks]

AGS does not go by numbers alone. Their grading is also based on light performance. Many online vendors with stones in house will tell you all you need to know about a stone. They take the guesswork out of it for you so that you don't have to worry about the variances in angles.

 

[new4diamond]

The angles which are considered 'ideal" depends on the size of the table:
http://www.agslab.com/docs/pbcg/AGSLProportionCharts.pdf

No, that is not was I was asking....maybe if I explain in this manner. I will use this example.

On this example of a diamond, would GIA grade this an Excellant cut, 34.9 Crown & 40.9 Pavilion...the Sarin report shows the Crown angles range from 34.3 to 35.5 and Pavilion range from 40.2 to 41.6....you get averages that grade Excellent, however are angle variations tight enough to get the grade.

 

[Karl_K]

I didn't want to post here without proof and I don't have time to dig up my files but since no one else has with some numbers.
Pavilion angles:
GIA 1+ degree plus on several occasions.
AGS one freak stone that was over 1 but in general I want to say .6 ish and above would not get 0 on a regular basis.
Crown: well over 1 for both gia and AGS maybe 3+ depending.
Crown variation has less effect than pavilion.

34.3 to 35.5 and Pavilion range from 40.2 to 41.6 would be almost guaranteed to be a bad scan with some dust under the stone.

 

[new4diamond]

I didn't want to post here without proof and I don't have time to dig up my files but since no one else has with some numbers.
Pavilion angles:
GIA 1+ degree plus on several occasions.
AGS one freak stone that was over 1 but in general I want to say .6 ish and above would not get 0 on a regular basis.
Crown: well over 1 for both gia and AGS maybe 3+ depending.
Crown variation has less effect than pavilion.

34.3 to 35.5 and Pavilion range from 40.2 to 41.6 would be almost guaranteed to be a bad scan with some dust under the stone.

Thank you for the reply...I have seen a couple of Sarin scans where both the Crown & Pavilion have varied as much as .6 degrees and got an AGSL Ideal cut grade. I just wondered how wide it can get to still get a Excellent cut from GIA or Ideal cut grade from AGS.

 

[Karl_K]

With AGS if the light performance test says its ideal its ideal LP no matter the numbers.
Everything else is in range and it gets the overall grade.
This leads at time to some really weird combos getting 0 but they are not the norm and just lucked into the grade.

For that reason I am very hesitant to give solid numbers because someone will come up with an exception.