How to interpret degree range on crown and pav angles?

[aflac]

Should I be concerned about the degree range on the crown and pavilion angles for the following diamond?

These are the specs on a 1.506 diamond.

It was rated an AGS Grade of 1 in the Sarin Report because of the crown angle. On the HCA it was rated .6 and Excellent on all dimensions.


AGS
Total Depth: 60.1%
Table: 55.9%
Crown: 33.1 degrees (30.2-35.0 degrees) 14.4%
Pavilion: 40.9 (39.5 - 42.2) 43.2%
Culet: .4% Very Small
Girdle: 1.5% (.9%-1.9%) (Thin-Sl. Thick)

GIA
Symmetry: Very Good
Polish: Excellent

 

[valeria101]

I don't think there is a standard way to interpret these. You could just look to a few certs of AGS0 diamonds and see if the numbers are "tighter" or not.

There are quite a few such documents and complete sarin reports posted here and there and you could definitely fidn enough ref. on GoodOldGold (just for everything, actually).

It seems that the min coresponds to the mid of the upper girdle facets (where the girdle gets it's thickest) and the max to the upper girdle joints (where the girdle is the most thin). The variation may not represent teh symmetry of cutting, just the simple fact that diamonds are not cut as a cone, but have more complicated shapes, and these measurements are too precise for their own good

 

[jesrush]

Should be a fine diamond! More brillant than firey, but sufficient fire for most people. I wouldn't be concerned!

-J

 

[jesrush]

Though I just noticed the variance behind those averages... that's quite a range, much more than normal:

Crown: 33.1 degrees (30.2-35.0 degrees) 14.4%
Pavilion: 40.9 (39.5 - 42.2) 43.2%

Hmmmmmmm....

I guess without a megascope to show you exactly how many crown\pavillion facets are at unusually high/low angles, there's no way to tell whether the individual facet angles are grouped around those averages (33.1\40.9) or whether they're wildly all over the place.

On second thought, I think I would pass on this stone. There are plenty of similar stones with normal variances.

-J

 

[valeria101]

So... here (LINK) is one piece that GIA considered of "excellent" symmetry and Isee2 gives it a 9.8 score (max that is).

The angle variations read (

):

Crown: avg 34.3 (min 34.2, max 34.4)
Pavilion: avg 40.9 (min 40.8, max 40.9)



Another (LINK) with more average symmetry and the Isee2 score below 6 reads:

Crown: avg 34.8 (min 32.8, max 35.5)
Pavilion: avg 42 (min 41.8, max 42.4)

 

[aflac]

Thank-you all so much for the great advice and information.

Based on the information I decided to pass on the diamond because I agree with Jesrush that there are many better diamonds out there.

 

[Garry H (Cut Nut)]

How could GIA call that "very Good"

 

[Paul-Antwerp]

Very weird stone.

That variance is enormous, and is definitely a big minus on the stone.

On the other hand, I wonder how this stone could be cut, with such a variance and still a straight girdle and a very small culet. Culet and table must be very much off-center.

I suspect that something is wrong with the Sarin-measurement.

Live long,

 

[Garry H (Cut Nut)]

You are right Paul - some dirt on the table and stone is not sitting flat!

 

[Paul-Antwerp]

Or maybe the suction-device of the Sarin was not working, and they used some paste to make sure that the diamond did not move during the measurement.

I can even imagine someone doing that, in order to save on the expense of having the Sarin fixed.

Live long,