steep deep

[nycmb404]

Now that I am familiar with the steep deep issue, what are the true "ideal" measurements on a round cut? What should I be looking for in order to avoid the issue? Any other things?

(I apologize if this has been covered in another thread, but I wasn''t able to find it.)

Thank you for your help.

 

[tyty333]

Here is the cheat sheet that lorilei usually post...

depth - 60 - 62% - although my personal preference is to allow up to 62.4%
table - 54- 57%
crown angle - 34- 35 degrees
pavilion angle - 40.6- 41 degrees
girdle - avoid extremes, look for thin to slightly thick, thin to medium etc
polish and symmetry - very good and above

note - with crown and pavilion angles at the shallower ends ( CA 34- PA 40.6) and steeper ( CA 35- PA 41) check to make sure these angles complement in that particular diamond - eyeballs, Idealscope, trusted vendor input - check as appropriate!

As the above implies, configurations depend on each other. A little give here can still work with a little take there.

From expert John Pollard.

With that said, here''s a "Cliff''s Notes" for staying near Tolkowsky/ideal angles with GIA reports (their numbers are rounded): A crown angle of 34.0, 34.5 or 35.0 is usually safe with a 40.8 pavilion angle. If pavilion angle = 40.6 lean toward a 34.5-35.0 crown. If pavilion angle = 41 lean toward a 34.0-34.5 crown.

GIA "EX" in cut is great at its heart, but it ranges a bit wider than some people prefer, particularly in deep combinations (pavilion > 41 with crown > 35).

 

[Lorelei]

Thanks Ty!

 

[stone-cold11]

Or just use the cut adviser. You will soon see a pattern.

https://www.pricescope.com/cutadviser.asp

 

[Lorelei]

Date: 11/18/2009 2:24:24 PM
Author:nycmb404
Now that I am familiar with the steep deep issue, what are the true 'ideal' measurements on a round cut? What should I be looking for in order to avoid the issue? Any other things?

(I apologize if this has been covered in another thread, but I wasn't able to find it.)

Thank you for your help.

As well with the numbers Ty posted always get Idealscope images particularly for borderline angle combos, if the overall cutting precision isn't tight and a few other factors are questionable, images are the single most important way to judge any diamond for what matters with steep deeps - light leakage.

Some diamonds which are hovering around steep deep range can be perfectly fine in some cases, others may not be so images are always needed, otherwise you could be dismissing a perfectly good diamond.

 

[nycmb404]

Thank you all for the very helpful guidance. In a previous post, I mentioned I was considering a stone (Round,1.29, F, SI1, Ex. Cut) with the following measurements:

Depth: 61.5
Table: 58
Crown: 35.5'' (15.0%)
Star: 50%
Pavilion: 41.0'' (43.0%)
Lower half: 80%
Girdle: Med-Sl.thk, facted 3.5%
Culet: none
Polish: ex
Symmetry: ex
After you pointed out the potential issues with the steep deep measurements, I went back to look at it (and another one I had referred to). I didn''t notice any issues that you described, and I did look at it in different lighting conditions (e.g., in the store, outside, in a darker area). The salesman showed me how it looked in a hearts and arrows gadget (I am sure that''s not the proper name), and it looked good, although I didn''t quite know exactly what to look for.

With this being said, do you guys have any additional thoughts on it?

 

[Lorelei]

Date: 11/18/2009 3:21:01 PM
Author: nycmb404


Thank you all for the very helpful guidance. In a previous post, I mentioned I was considering a stone (Round,1.29, F, SI1, Ex. Cut) with the following measurements:

Depth: 61.5
Table: 58
Crown: 35.5' (15.0%)
Star: 50%
Pavilion: 41.0' (43.0%)
Lower half: 80%
Girdle: Med-Sl.thk, facted 3.5%
Culet: none
Polish: ex
Symmetry: ex


After you pointed out the potential issues with the steep deep measurements, I went back to look at it (and another one I had referred to). I didn't notice any issues that you described, and I did look at it in different lighting conditions (e.g., in the store, outside, in a darker area). The salesman showed me how it looked in a hearts and arrows gadget (I am sure that's not the proper name), and it looked good, although I didn't quite know exactly what to look for.

With this being said, do you guys have any additional thoughts on it?

It could be ok depending on the precision of the cut and angle averages, really an Idealscope image would be better than a h&a scope as the IS shows leakage, ask the seller if they have an Idealscope, they might do. See if you can take it outside or look at it in dim lighting - you could try under a desk. Watch the diamond to see if it shrinks or you can see any dark dull patches around the table or a dark ring around the table.

 

[FB.]

Date: 11/18/2009 3:21:01 PM
Author: nycmb404


Thank you all for the very helpful guidance. In a previous post, I mentioned I was considering a stone (Round,1.29, F, SI1, Ex. Cut) with the following measurements:

Depth: 61.5
Table: 58
Crown: 35.5' (15.0%)
Star: 50%
Pavilion: 41.0' (43.0%)
Lower half: 80%
Girdle: Med-Sl.thk, facted 3.5%
Culet: none
Polish: ex
Symmetry: ex


After you pointed out the potential issues with the steep deep measurements, I went back to look at it (and another one I had referred to). I didn't notice any issues that you described, and I did look at it in different lighting conditions (e.g., in the store, outside, in a darker area). The salesman showed me how it looked in a hearts and arrows gadget (I am sure that's not the proper name), and it looked good, although I didn't quite know exactly what to look for.

With this being said, do you guys have any additional thoughts on it?

35.5/41.0 is on the borderline of steep/deep.
If the effect is there, it would show as a dark ring inside the table edges, when viewed from a perfect face-on angle. Tilt the stone slightly and the dark ring disappears.

I have a 35.5/41.2 that manages to get away with being "steep deep" because of a few small cutters tricks - and rounding-up of numbers on the GIA report.
The actual stone proportions are closer to 35.25/41.1, with 56 table and 62.8 depth.
Only occasionally, under close scrutiny, viewed from directly above, in the correct lighting, (knowing what I'm looking for) can I *maybe* see a very slight dulling around the edge of the table.

If you're able to put it in an environment where only light can enter from the top of the stone, you might then have more chance to see a dark ring.

 

[nycmb404]

Thank you Lorelei and FB.

I have not noticed the effect even outside and when I looked at it under a desk, but I will double check to see how it looks in much darker light.
I have seen some discussion about steep deeps also appearing smaller than they should for their carat weight. Should this be a concern on this particular stone?

 

[Lorelei]

Date: 11/18/2009 4:00:33 PM
Author: nycmb404
Thank you Lorelei and FB.

I have not noticed the effect even outside and when I looked at it under a desk, but I will double check to see how it looks in much darker light.
I have seen some discussion about steep deeps also appearing smaller than they should for their carat weight. Should this be a concern on this particular stone?

I just went back and checked the diameter of this diamond, assuming it is the 1.25 from the other thread the diameter is fine, maybe a hair less but nothing to worry about.

 

[nycmb404]

Sorry, I was referring to the 1.29 , rather than the 1.25. I liked the look of the 1.29 better after comparing the two.

 

[Lorelei]

Date: 11/18/2009 4:28:32 PM
Author: nycmb404
Sorry, I was referring to the 1.29 , rather than the 1.25. I liked the look of the 1.29 better after comparing the two.

Ok thanks, do you have the diameter for the 1.29 please?

 

[nycmb404]

It''s 6.95 - 6.99 x 4.29 mm

 

[Lorelei]

Date: 11/18/2009 4:35:08 PM
Author: nycmb404
It''s 6.95 - 6.99 x 4.29 mm

Thanks, the diameter is fine.

 

[stone-cold11]

Ideally, should be around 7.03mm, so not much difference, most are cut around this diameter anyway.