Is this a good cut?

[shopper9]

Hi everyone- Would you be so kind as to critique this diamond? Based on what I''ve read, this is slightly out of the ideal range for a well cut diamond, but only just. I''m wondering if these small margins will make a big difference, or whether this will still be a very sparkly diamond? This is a GIA certified stone.

Stone 1:

Carat weight: 0.55ct
Colour grade: J
Clarity grade: SI1
Cut grade: Excellent
Measurement: 5.23-5.25x3.28mm
Clarity characteristics finish: crystal, feather,cloud finish
Polish: excellent
Symmetry: very good
Fluorescence: none.
Depth: 62.8%
Table: 58%
pavilion angle: 41.4 degree
crown angle: 35.5 degree
Girdle: medium to slight thick

Thanks guys!

 

[shopper9]

Forgot to say that this is a round cut diamond.

 

[Lorelei]

Date: 7/8/2009 7:16:08 AM
Author: shopper9
Forgot to say that this is a round cut diamond.

Hi shopper

No it isn't a good diamond, too deep and bad angles which could lead to considerable light leakage and a dull diamond which doesn't sparkle much. Yes the proportions are crucial in order for you to have a well cut sparkly stone, this one won't be a beautiful diamond very likely.

 

[stone-cold11]

ya, angles are too far off the ideal range. Give this stone a miss.

 

[phoenixgirl]

No, unfortunately with a higher pavilion angle (41+), you need a lower crown angle (more like 33-34). Conversely, with a higher pavilion angle (35+), you need a lower pavilion angle (more like 40). Because these angles by themselves can result in a beautiful cut, the GIA can give a grade of excellent to a stone that actually has the right parts but not the right parts for the other angles, if that makes any sense. AGS is more discerning in giving an ideal grade to stones, so generally with AGS0 ideals you can be confident that the angles work with each other, at least on paper. And as long as you know the crown and pavilion angles, you can run them through the Holloway Cut Adviser (under Tools up top) to see how the angles work with each other. Then seeing the stone in person or at least an Idealscope or ASET image is the next step.

Good luck!

 

[shopper9]

Thanks for all the feedback. I''m quite amazed that a stone that is only slightly outside of the recommended values can be so bad. So i''m guessing that being inside the values below is not enough to be a good cut. the values are reliant on each other, so its not a hard and fast rule to find a stone within these ranges:

depth - 60 - 62.4% ( my personal cutoff.)
table - 54- 57%
crown angle - 34 - 35 deg
pavilion angle - 40.6 - 41 deg
polish and symmetry - very good and above
girdle - avoid extremes look for thin to slighly thick, thin to medium etc.

I will stay clear of this particular diamond, and will aim to find an AGS0 one if poss- it sounds like these have a much better cut standard.

Thanks alot forum peeps.

 

[Lorelei]

Try these proportions as a guide,

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!

From expert John Pollard.

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

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).