Excellent vs Very Good GIA Cut, but 0.9 HCA

[aub]

Hi All, I have been looking for a little while and beginning to understand the importance of the cut.

I am interested in a stone and all other C''s aside (which I am happy with) the cut grading is Very Good by GIA. It appears that the reason it missed Ideal was the CROWN angle is just below the GIA range (~33.5 to 35 I believe) for Ideal.

However HCA grading gives it a 0.9 with Excellent for all factors Light Return, Fire, Scintillation and Spread. So it''s obvious that there are other factors besides these that GIA considers. Can the experts here help me understand what else I should be looking for and what I might be compromising?

 

[stone-cold11]

Can you give the numbers you used to input in the HCA? Also girdle thickness, star and LGF numbers?

EDT:
Or just give the GIA report number.

 

[aub]

Round Cut
59.6% depth, 58% table, 32.5° crown angle, 40.8°
Girdle: TN-STK
LGF Number: ? (Not familiar and does not say on the report)

The report scan isn''t a good one and I''m having trouble reading out the report numbers. Is the information above close?

Thanks!

 

[stone-cold11]

This stone has a shallow pavilion angle for it''s crown angle. On the cut adviser, it is plotted just lower outside of the range of angles of what GIA considered to be GIA excellent. There could be some obstruction issue with this stone, which means that it could appear darker if you viewed closer than 10 inches away but if viewed further than that distance, normal viewing distance, it will be bright and lively. An Idealscope image will confirm if this will happen. Can your vendor supply one?

 

[Lorelei]

Date: 5/20/2009 6:44:38 PM
Author: aub
Round Cut
59.6% depth, 58% table, 32.5° crown angle, 40.8°
Girdle: TN-STK
LGF Number: ? (Not familiar and does not say on the report)

The report scan isn't a good one and I'm having trouble reading out the report numbers. Is the information above close?

Thanks!

Actually it has potential, I don't think obstruction will be an issue as this normally happens with a matching shallow pavilion angle, the crown is only slightly shallow anyway. The proportions suggest this will be a very bright and brilliant diamond, but fire could be down somewhat. Ask if you can get an Idealscope image for this diamond, that will tell us more.

 

[aub]

Wish I could, but the stone got sold the same day after my post. Back to square 1.

 

[Lorelei]

Date: 5/25/2009 12:36:57 AM
Author: aub
Wish I could, but the stone got sold the same day after my post. Back to square 1.

I am sorry, you will find the one!