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1.58ct round F, Si1 - priced ok?

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danrts

Rough_Rock
Joined
Jun 18, 2009
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Hi, I''m new here and I''m thinking of purchasing this diamond for ~ $11,000. Does this seem a reasonable price for the specifications?


Certificate: GIA
Shape: Round
Cut: Excellent
Carat: 1.58
Color: F
Clarity: SI1

Diamond Proportions:
Measurements: 7.52-7.47-4.64
Depth Percentage: 61.9 %
Table Percentage: 56 %
Girdle: TN-M
Culet: None (Pointed)
Polish: Excellent
Symmetry: Excellent
Fluorescence: None (Inert)
 
What are the crown and pavilion angles?
 
thanks for the reply. who would inscribe H&A on the girdle? is this the diamond cutter or the jewellery store? or is it a patented inscription that a particular "brand" or company does?
 
Probably the diamond cutter but who knows? Can be anyone who have access to the stone. GIA just reports what is there.
 
Hi Stony, this is approximately the same price, does this look better on specs: (I note it's considered 1.6ct but the dimensions are actually less than the first mentioned stone, that's considered a 1.58ct - so is this a miss-sizing of the diamond?)

Round Brilliant (GIA certified)
Measurements: 7.47 - 7.50 x 4.64 mm

Carat Weight: 1.60 carat
Color Grade: F
Clarity Grade: SI1
Cut Grade: Excellent

Proportions:
Depth: 62.0%
Table: 57%
Crown Angle: 34.5°
Crown Height: 15.0%
Pavilion Angle: 41.0°
Pavilion Depth: 43.5%
Star length: 50%
Lower Half: 85%
Girdle: Medium to Slightly Thick, Faceted (3.5%)
Culet: None

Finish:
Polish: Excellent
Symmetry: Excellent
Fluorescence: None
 
Number is slightly safer but I would prefer a 40.8 pavilion angle for that crown angle if buying blind. But if it is from USACerted too, they should be able to get you an IS image, just ask them for it.

The dimensions are ok, cutting is slightly different and the dimension difference is not that large anyway. Both min diameter is 7.47mm, max just different by 0.02mm?
 
Hi dabrts,

Are these diamonds with a jewellery store or online vendor? Both have crown and pavilion angle combinations which might not be the best balance for each other, so if these are online then an Idealscope image would be very useful. If you are unfamiliar with Idealscope, this page explains.

http://www.highperformancediamonds.com/index.php?page=education-performance

Also it is important to know, what are the grade making inclusions for the SI1 clarity grades such as feather, clouds etc? If clouds are grade makers then careful checking will be needed to make sure they don't interfere with brilliance.

As to the inscription, no way of knowing who had the diamond inscribed, could have been the supplier. Also if you want a h&a cut then images of the hearts and arrows are needed.
 
Hi, they're from online jewellers, bluenile and union diamond. I'm asking for idealscope image to see what they come up with. I've looked at the GIA certificates, and on one of the certificates, it says "Clouds are not shown". On the other, bluenile, catalog # LD01282242, the GIA certificate is a bit grainy so the clouds are shown but I can't really see where they are.
 
Date: 6/20/2009 5:16:29 PM
Author: danrts
Hi, they're from online jewellers, bluenile and union diamond. I'm asking for idealscope image to see what they come up with. The GIA certificates on their websites indicate where the inclusions are but not being an expert I'm not sure if the brilliance is affected.
Click to expand...
The main thing to watch for with SI clarity grades is if clouds are plotted on the clarity plot as grade making inclusions - the reason that a particular diamond is of SI1 or SI2 clarity is because there is a cloud present in the diamond and marked on the plot. This is different to in the comments section if it says ' clouds not shown' or 'additional clouds not shown', these are not an issue, but a cloud which is noted on the clarity map could be. If so just make sure the vendor checks that the cloud is not interfering with the brilliance of the diamond.

Here is an example if you click on the link then on the GIA report. If you look at the diamond diagram and the list of inclusions beneath it, you will see second one down is a cloud. This would need checking with the vendor as above.

You will see in the comments section that ' additional clouds not shown' are mentioned, as above this isn't an issue usually.

http://www.jamesallen.com/diamonds/G-SI1-Premium-Cut-Round-Diamond-1104120.asp?b=16&a=12&c=77&cid=131
 
Thanks for the advice. I''m wondering out of curiousity, how many GIA graded cuts as "excellent" actually return a poor ASET or a poor Idealscope image, as I thought a GIA cut of "excellent" was meant to mean most light gets reflected back as opposed to it leaking etc.
 
Quite a lot apparently. This is because of the way a round is cut. GIA Ex grade allows for quite a large pavilion angle and if a cutter can get an Ex grade and still retains much of the original rough diamond weight, he will do it as that allows for a much higher price for the cut stone.
 
Thanks, I''m now wondering about the reverse, what the likelyhood is of a GIA cut grade of "very good" then produces an "excellent" ISET or idealscope image. Now that would be a better bang for buck!
 
Yap. Use the cut adviser to check them out.

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

Best is the get the angles within the AGS0 range but out of GIA Ex range. Going too shallow with the pavilion angles will result in obstruction issues. Read the usage warning and information page on the result page of the cut adviser for more information. Usage warning and information page
 
Stony, thanks for the info about the HCA index.

The 1.58ct listed above gives a HCA number of 2.3 - VG/VG/VG/VG. the GIA rating on this is cut EX, polish Ex, symmetry Ex.

I''ve now found a 1.56ct (7.49x7.53x4.56) depth 60.7, table 58, crown angle 35, pavillion angle 40.8 which gives a HCA number of 1.6 - VG/EX/EX/VG. But the GIA rating on this is Cut Ex, polish - VG, symmetry EX.

My question is, would you got for the 1.56ct with a lower HCA number, at the expense of the polish being VG (rather than excellent in the 1.58ct)?
 
Yes, I would, but I would still like to see the IS/ASET image before deciding. :P. VG/EX polish is indistinguishable by normal people.
 
Date: 6/20/2009 5:31:36 PM
Author: danrts
Thanks for the advice. I''m wondering out of curiousity, how many GIA graded cuts as ''excellent'' actually return a poor ASET or a poor Idealscope image, as I thought a GIA cut of ''excellent'' was meant to mean most light gets reflected back as opposed to it leaking etc.
Click to expand...
GIA Excellent cut grade allows for what we call steep deep angled combos to get the Ex cut grade, this means that the crown and pavilion angles don''t work well together resulting in light leakage, so each GIA Excellent needs careful evaluation.
 
Date: 6/20/2009 8:38:53 PM
Author: danrts
Stony, thanks for the info about the HCA index.

The 1.58ct listed above gives a HCA number of 2.3 - VG/VG/VG/VG. the GIA rating on this is cut EX, polish Ex, symmetry Ex.

I've now found a 1.56ct (7.49x7.53x4.56) depth 60.7, table 58, crown angle 35, pavillion angle 40.8 which gives a HCA number of 1.6 - VG/EX/EX/VG. But the GIA rating on this is Cut Ex, polish - VG, symmetry EX.

My question is, would you got for the 1.56ct with a lower HCA number, at the expense of the polish being VG (rather than excellent in the 1.58ct)?
Click to expand...
Actually you will not notice any difference between good and above for polish and symmetry with the naked untrained eye. The 1.56 diamond definitely warrants an Idealscope image with that angle configuration as it is borderline steep deep as above.
 
I've uploaded the idealscope for the 1.58ct that returned a HCA score of 2.3 . but I'd be please with some advice now I got the idealscope image!

1-58a.jpg
 
1.58ct HCA score 2.3 - 2nd idealscope image

1-58b.jpg
 
Looks like some slight leakage under the table. Might not be noticeable in real life. Do you have the IS for the 1.56c?
 
hi Stony, I''m trying to get the IS for the 1.56ct. But gGven a HCA score of 2.3 and the IS images you see for the 1.58ct, if you didn''t know the HCA score for the 1.58ct do the IS images look excellent/very good/good/fair/poor in your expert eyes?
 
VG only.
 
Date: 6/22/2009 9:17:31 PM
Author: danrts
hi Stony, I'm trying to get the IS for the 1.56ct. But gGven a HCA score of 2.3 and the IS images you see for the 1.58ct, if you didn't know the HCA score for the 1.58ct do the IS images look excellent/very good/good/fair/poor in your expert eyes?
Click to expand...
danrts, we are not experts, just consumers. It is important to reiterate that so that everyone who reads understands the source of where the advice is coming from. The IS image is actually very good, tiny amount of leakage should not be visible to the naked eye. This diamond is far better cut than many you will find.
 
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