HCA Question - and stone for your evaluation

[bostonkiddo]

Hi all, thanks for your help last week -
- so, the verdict that came down from you super-helpful experts was that I really needed to watch out for shallow stones with large spreads, even if they score well on HCA because they may/will have obstruction issues. This makes sense and I appreciate all the clear advice I got.

I've been playing around with proportions and I am still curious about how the HCA treats possible obstruction. It seems that of the 4 categories (light return, fire, scintillation, and spread), ex,ex,ex,vg combos are seen as quite desirable. Again, this makes perfect sense. However, I haven't seen any expert-recommended stones with HCA <2 and ex spread (and it is possible that this is because I've only been following the forums for a few months). It seems that obstruction is brought up as an issue whenever the stone gets an ex for spread on the HCA. Is it possible to get an HCA <2 with ex spread and no obstruction issues, or does this mean that ex spread should only be reserved for pendent/earring stones? As a relative newbie (albeit one apt to do lots of homework), this information would be a great addition to the education materials already provided on this site.

On a completely separate note:
This diamond is priced very reasonably and I am waiting on IS images and photos, but I think it may be a good choice. Again, GIA did not list it as excellent, but it scores very well on HCA and I asked the vendor to look into the reasons for its downgrade - I suspect brillianteering of some sort.

Based on the proportions, do you think this is promising?

D 61.9
T 54
Crown 34
Pav 40.6
star 50%
lower half 85%

Girdle m-sltk
Polish ex
Sym ex
culet none

HCA .7 (TIC)

Thanks!

ETA: sorry about forgetting carat/dimensions
6.95 - 7.01 x 4.32 mm
1.29 carats

 

[FB.]

I suspect that the 85% lower half is the main reason for the downgrade, although brillianteering is possible.
Strangely, some GIA certs with lower-than-expected-cut-grade mention brillianteering and others don't - even though some that don't mention it have perfect proportions but the stone has very obvious tweaks.

The greater lower half % will partially offset any obstruction issue and also partially offset the under-table darkness of the arrows that can be associated with the small-ish table. It would appear to be an excellent stone that's worthy of serious consideration.

To score "EX" on HCA for spread, you only need to have depth 60.3% or less. There are a few stones with TIC angles and/or thin girdles and/or large-ish tables, that can be found to have that depth and ideal angles.

 

[Lorelei]

Date: 12/7/2009 12:32:13 PM
Author:bostonkiddo
Hi all, thanks for your help last week -
- so, the verdict that came down from you super-helpful experts was that I really needed to watch out for shallow stones with large spreads, even if they score well on HCA because they may/will have obstruction issues. This makes sense and I appreciate all the clear advice I got.

I've been playing around with proportions and I am still curious about how the HCA treats possible obstruction. It seems that of the 4 categories (light return, fire, scintillation, and spread), ex,ex,ex,vg combos are seen as quite desirable. Again, this makes perfect sense. However, I haven't seen any expert-recommended stones with HCA <2 and ex spread (and it is possible that this is because I've only been following the forums for a few months). It seems that obstruction is brought up as an issue whenever the stone gets an ex for spread on the HCA. Is it possible to get an HCA <2 with ex spread and no obstruction issues, or does this mean that ex spread should only be reserved for pendent/earring stones? As a relative newbie (albeit one apt to do lots of homework), this information would be a great addition to the education materials already provided on this site.

On a completely separate note:
This diamond is priced very reasonably and I am waiting on IS images and photos, but I think it may be a good choice. Again, GIA did not list it as excellent, but it scores very well on HCA and I asked the vendor to look into the reasons for its downgrade - I suspect brillianteering of some sort.

Based on the proportions, do you think this is promising?

D 61.9
T 54
Crown 34
Pav 40.6
star 50%
lower half 85%

Girdle m-sltk
Polish ex
Sym ex
culet none

HCA .7 (TIC)

Thanks!

Normally shallower depthed stones of 60.3% or less will get Ex for spread.

The diamond in question will get VG cut grade because of the length of the lower girdle facets. These will give the effect of thin splintery arrows if the diamond has good optical symmetry and shows an arrow pattern, also this will give sharper thinner flashes of light, personally I like these types of diamond.

An Idealscope image will tell us more when you have it, obstruction is a possibility also depending on rounding issues but it could be perfectly fine, again the IS will let us know.

What is the carat weight and diameter for this diamond too please?

 

[stone-cold11]

Promising from the numbers, will wait for the IS.

 

[bostonkiddo]

ok, I heard back from Judah at Exceldiamonds, who has been very helpful so far. The IS, photo and ASET are under this link:


LINK

what do you all think?

I wasn''t planning on pulling the trigger on the purchase quite yet, but I could if this is a great deal. I REALLY like excel''s tiffany setting, so buying a stone from there would be a serious bonus, I am having a hard time deciding whether I will be able to get a better (read bigger with equal or better light performance) stone for the same amount.

I have a bit of wiggle room in the budget, but the jump up to 1.5 carats for a well performing stone is WAY too high as far as I can tell. I wonder if there will be better selections after the Christmas rush is over...

basically, parameters are:
Cut: Awesome (i promised her, jokingly, that I would get her a stone that was bigger and shined just as much as the T&C rings she loves...)
Clarity: Eye-Clean
Color: She couldn''t tell the difference between a D and an H in the store, so I think down to J should be OK.
Size: As large as possible

Stone Budget: 5,700 or so, but wouldn''t mind spending less.

Do you all think I can do better within my budget?

Thanks!