Help evaluate this diamond

[sparky_2304]

Hi guys,

I have been looking for a loose diamond for either a pendant or a ring for a while now and this is what I found interesting.Price is ~$6300. The stone has been graded as GIA Excellent cut but the HCA score is 5.4!! due to it being slightly too deep. I'm still not ready to pull the trigger yet, and I would really appreciate any input or advice. Is this a good/ok/bad deal?

GIA
6.97 - 7.00 x 4.38 mm
Weight: 1.32 carat
Color: I
Clarity: SI2
Cut: Excellent
Depth: 62.7 %
Table: 56 %
Crown Angle: 36.0°
Crown Height: 16.0%
Pavilion Angle: 41.0°
Pavilion Depth: 43.5%
Girdle: Medium to Slightly Thick, Faceted, 3.5%
Culet: None
Polish: Excellent
Symmetry: Excellent
Very Strong Blue Fluorescence
Verified eye clean

 

[teobdl]

You really need to get an idealscope on that. I may be mistaken, but it may be that even a perfectly but diamond w/ those specific proportions will have leakage.

 

[metatrix]

Verified eye clean? Really?? By whom...a severe myopic?

 

[Gypsy]

Pass.

You can do better.

 

[diamondseeker2006]

Definitely pass. I think the leakage is visible in the photo. Use the HCA as an elimination tool. It does usually work when it comes to diamonds that score this high. I'd consider ones that score under 2.5 and under 2.0 is safest of all.

Here are some parameters that will help you get a better stone:

table 54-58

depth 60-62.3

crown angle 34-35

pavilion angle 40.6-41.0

The one you posted is too deep, and that makes the stone face up smaller than it should. The angles pretty much mean there will be some leakage. Very strong fluorescence has to be evaluated as well. It could cause the diamond to be hazy at times, especially in an SI2 stone.

 

[sparky_2304]

Thanks for the replies! Attached are the Idealscope and ASAT images. I'm no expert at reading these. Do they show significant light leakage?

 

[metatrix]

Thanks for the replies! Attached are the Idealscope and ASAT images. I'm no expert at reading these. Do they show significant light leakage?

Yes, there is significant leakage.

Idealscope images tell you about light output and how the facets of the pavilion (bottom half of the diamond) are functioning -- are the facets acting as reflectors of light as they should, or are they acting as windows (allowing the light that enters the diamond to escape right through them and out the bottoms of the diamond)?

In the idealscope image you posted, the arrow shafts should be black like the arrowheads, instead of white. The white means that the pavilion mains, which are supposed to act as reflectors of light that enters directly through the top of the diamond (i.e. light entering at a perpendicular angle) in the diamond, are instead acting as windows, allowing the light entering the diamond to escape out through the bottom. That's bad, and it implies that overall light return, and therefore both brightness and fire, will suffer greatly. The area under the table around the arrows (corresponding to the upper girdles, which are supposed to reflect light from 45-75 degrees from the horizontal, which is the most intense source of light) also shows leakage. Basically, the entire bottom half of the diamond is failing to do its proper job. It doesn't matter how well the top half functions to let light into the diamond, because the bottom half is letting it leak right back out.

The ASET images tell you about light input and how the facets of the crown (top half do the diamond) are functioning to let light in. More specifically, it tells you from where (from what angle) the light is entering the top of the diamond.

In the ASET you posted, those arrow shafts should be blue (meaning the light hitting the pavilion mains should be coming from directly above, or perpendicular to the table), and instead they are red (meaning that the light is instead being drawn from 45-75 degrees from the horizontal). Now, I already told you that the most intense light source is from 45-75 degrees, so you may be thinking - isn't that a good thing? No -- for two reasons. Reason 1: light hitting the pavilion mains needs to come from directly above in order reflect the shadow of your head. This creates the black arrows contrast pattern characteristic of a modern brilliant diamond, and greater contrast actually enhances how bright the diamond looks because of how your visual cortex interprets light and shadow. These arrows of 'head obstruction' are also where you will see the broad flashes of fire under direct spotlighting. Since the arrows are not black, you won't see those broad fire flashes. Reason 2: remember that the idealscope told us that the pavilion mains were acting as windows instead of reflectors. So the fact that the most intense light entering the diamond is hitting the pavilion mains is doubly bad -- the brightest light from the environment is hitting the pavilion mains and then escaping right through them. And the rest of the area under the table (corresponding to the upper girdles) is once again white, representing severe light leakage, as you already saw from the idealscope image.

Thanks for posting those images -- they are an excellent example of how light enters and exits a poorly proportioned (but optically symmetric!) diamond.

(I think I got all of the above right, but I'm new to diamonds, so let me know, veterans, if my explanation was wrong!)

 

[OoohShiny]

All that white light in the latter image shows light escaping rather than being returned to you - you are effectively seeing through the diamond, as I understand it (?).


Definitely pass on that one!

 

[metatrix]

Sorry, whenever I wrote 'upper girdles' in my explanation above I actually meant to write 'lower girdles'. Tried to go back and edit, but couldn't. Sorry for the confusion.