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TNVOL

Rough_Rock
Joined
Feb 13, 2003
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5
I am evaluating two Ideal cut rounds, both are G color, VS2 clarity, one is slightly larger in dia and weight. Cost differences are negligible. One is a 0.6 on the Cut Advisor (an Ideal Cut from Blue Nile), the other (larger of the two) is a 1.4 (Cut Above H&A from WhiteFlash). The catch is the larger one (1.4 HCA) has a girdle that is half the thickness of the smaller one. My gut tells me that the 0.6 HCA combined with a thicker girdle makes the smaller stone the one to choose. As far as the appearance, beside each other they look virtually identical. I have looked at them under a 10X loupe as well as a 20X microscope. The H&A patterns on both stones are both very well defined and clear. Am I correct in going with the slightly smaller stone that scored 0.6 ?
 

TNVOL

Rough_Rock
Joined
Feb 13, 2003
Messages
5
HCA .6 Stone HCA 1.4 Stone
Table 56.6% (2.79mm) 54.2% (2.72mm)
Diameter 4.93mm 5.02mm
Depth 61.7% (3.04mm) 61.8% (3.10mm)
Crown 34.9 degrees 33.9 degrees
Pavilion 40.5 degrees 41 degrees
Culet 1.6% (.08mm) 1.4%
Girdle 3.2% (.16mm) 1.2%

What do you think ??
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,275
When you post information like this it is best to leave out *who* the stones are from because anyone giving advice feels like they are somehow taking sides with a vendor. At face value one would also be inclined to say the .6 but in this case I would advise against it and here's why.

If you are familiar with our internal cut analysis and the LightScope images you know it shows with great contrast the difference between the dark reds and the pale reds. I have been able to duplicate this within the Diamcalc software and here are 2 possibilities of what you may have. Now ... I DO NOT KNOW your star/lower girdle facet measurements which would give the complete picture so I through in random #'s for the stars and lower girdles which may indeed be wrong but possible. Any, and I repeat, ANY gemological information shared here should always be confirmed by a professional 2nd opinion.

As you can see in the .6 stone there are alot of pale reds under the table whereas in the 1.4 there are more dark reds under the table. I can point you to examples on my website showing live pictures and examples of such stones and how they tested in the optical analysis in real life but time does not permit. In short the 1.4 stone with it's presence of more dark reds is the stone I would suggest. (If you've read my page on how to interpret the images you'll know that more dark reds = more intense light return from within while more pale reds = weaker light return. Here is the page on that. http://www.goodoldgold.com/the_idealscope_firescope_tm.htm)

I am extremely busy at this time but had a few mintues to answer this before going up to work. Hope this helps.

Rhino

RICKCOMPARE.gif
 

TNVOL

Rough_Rock
Joined
Feb 13, 2003
Messages
5
Thanks for the input. I only "branded" the stones because both vendors "brand" their cuts so I thought that may spark some extra info. I have been looking again at both stones and I believe the 1.4 HCA stone does appear a bit more sparkly (for lack of a better adjective). Prior to plugging the Sarin numbers into the HCA, my gut was to pick the 1.4. My only concern is the thin girdle, I'd hate to see it chipped when being set or when being worn. Am I being overly uptight about that ? What's the concensus on the girdle thickness?
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
What do the certificates say on girdle thickness, I know you posted the % but what does that translate to in the way of thin, medium, thick etc. If it says Medium or Thin to Medium or Thin to Slightly Thick then you should be fine. Slightly Thin to Thick or Slightly Thin to Thin may be something to stay away from.

Personally I think the .6HCA stone's average girdle % looks too big (3+%). From what I have seen in my searches, the ideal range of a girdle should fall more into the .7-2.9% range. I found a picture on Rhino's website that has this mapped out a bit as well and has this as the range for a technically ideal cut. Obviously the range will vary as the girdle thickness % is relative to the diameter of the stone itself. But I think a 3+% girdle may be a little too thick.

My girdle is slightly thin to slightly thick...but it is a little thin in some areas and combined with the shallow crown angle of my stone, it led CutNut to think it may be prone to chipping. However...other people have told me that chipping is more rare than it may seem...and we are getting insurance anyway to be sure to protect the stone just in case. I don't have my diamond's specs with me, but I think my girdle was around the average of 1.2% as well, but keep in mind that my crown angle was under 30 degrees, while yours is in the ideal range, so the chipping may not be an issue. Cut Nut?

Also just from my own personal opinion and preference, I would hands down choose the A Cut Above SuperIdeal stone over Blue Nile! I know that alot of people like BN, but they are a mainstream jewelry company and offer only the basics on most of their stones. Do they have an IdealScope image of the stone like WhiteFlash does on it's stones? Do they offer any BScope readings or even acknowledge the HCA etc? Sure they offer some specs on their Signature Ideal stones like an AGS report and maybe H&A images, but why not give the same info on their 'regular' stones. Just because they actually went the extra mile for these 'Signature' stones they feel they can charge more of a premium just because they bothered to do the work to give the consumer more info...therefore pushing you more towards their Signature Ideal line than their regular lineup if you are seeking the illusion of top quality. At least the ACA branded stones appear to offer nearly perfect IS and H&A images so in my mind they have the right to brand their stones something special and charge a bit of a premium. Even the ACA premium is not as overpriced as the BN stones have seemed to be in the past.

I'll stop my rant there...but I definitely like the 1.4HCA stone better. Doesn't hurt that it is bigger.
Both stones are still extremely excellent, less than 5% of the diamonds out there fall into that category of under 2.0HCA, so both are great picks most likely. Go with your gut!
 

TNVOL

Rough_Rock
Joined
Feb 13, 2003
Messages
5
Hi Mara,

The 1.4 HCA stone's AGS cert says faceted 0.8-1.4%
The 0.6 HCA stone's AGS cert says faceted 1.4-2.4%
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
Oh sorry--in your spec post you had the girdle at 3.2% average which was high I thought...but the average looks to be more like 1.6/1.8? More acceptable!!

Does it say medium or thick or slightly thin ? Any association besides the %%?
 

TNVOL

Rough_Rock
Joined
Feb 13, 2003
Messages
5
Mara,

The HCA 0.6 stone has an AGS cert that calls out 1.4-2.4%. There is also a GCAL appraisal that calls out 3.2% (.16mm).

The HCA 1.4 stone has an AGS cert and a Sarin report that pretty much agree with each other.

I do know that when I put the two stones under a microscope, I can read the laser etch on the 0.6 girdle very easily in comparison to the 1.4 stone.
 
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