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HCA, angle vs % makes a big diff.

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gdog

Rough_Rock
Joined
Jan 27, 2003
Messages
2
Hi there. So I have finally narrowed down to a stone I want... and hopefully afford. I put the numbers into the HCA and found it to be sadly above a 2. It is a 1.51ct AGS 0 (Id/Id/Id), G, VVS1. I have negotiated down to just under 14k. I am pretty happy on that, plus it is a Canadian stone, which is important to me (a Canadian marrying an American).

Now the question comes on the HCA. The specifics of the stone are:
D: 60.8
T: 56
C: 34.8 (15.3%)
P: 41.1 (43.4%)
Pointed Culet
Girdle is 0.9-1.5%

On the HCA, this comes out to 2.1 (VG/VG/VG/VG)

Now if I enter the percentages, instead of the angles, it comes out to 1.5, in the TIC scale.

Am I just nit picking here or is this still a killer stone? All I wanted was a quality cut, size is bonus.

Thanks for the input. E-Day is nearing!
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
Not to nitpick but I ran the #'s and got a 2.2 on the HCA. Anyway...anything under 2.0 on the HCA is excellent. Your stone is 2.2. Is that really much of a difference? Would you be happier if it was 1.9? The difference seems minimal.

If you have seen this stone, like it, feel comfortable with the price, the HCA is just a bonus. A stone graded an A+ on paper that does not speak to you is not worth the A+ rating. A stone can be graded an A- on paper, but if you love it, it's pretty much still a strong A in my book! Okay so my analogy doesn't make much sense, but its late and I'm tired. You get my point.


On the angles vs. percentages, there are tons of threads on this...angles are much more accurate than percentages which are usually rounded and do give alot more of a range when plugged into the HCA. Many examples of this have been posted in past threads...e.g. my stone is a 1.7 with percentages but with angles its a 2.5. I was bored today at work and ran some EGL certs from eBay and one was a 2.7 with angles but a 1.9 with percentages (they had both the EGL and a sarin i think). Anyway, angles are much more accurate. But basically if with % your stone is a 1.5 and with angles its a 2.2--you can always average out the difference and you get 1.8/1.9! Still under 2.0. Does that make you feel better?


Bottom line is I think you are fine. From eyeballing the #'s below, IMO your depth seems just a tad bit deep for the crown, and it is carrying that tiny bit of extra weight in the pavilion..but just by a hair. Then again I'm not an expert...I'm still learning too.

I would suggest..if you like the stone and have made it this far, get it! Sounds like everything is in place except the HCA score and we are not talking a 4.1 or even a 3 on the HCA..this is a 2.2. Still pretty good. I bet you will see no visual difference between this stone and a 1.9 TIC.

Good luck, whatever you choose!
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,317
41.1 degrees = 43.6% not 43.4%
Sarin and Ogi measure angles better than %'s.

This extra 0.15 degrees is in a critical region. It will push most slightly unsymmetric stones into bad leakage, and most symmetric stones in to more leakage than someone hunting for an exceptional cut should accept.
 

gdog

Rough_Rock
Joined
Jan 27, 2003
Messages
2
I don't quite follow "41.1 degrees = 43.6% not 43.4%", I pulled the 41.1 off of the AGS cert. Did they use the lower end of the girdle?

I have read all the tutorials I have found on the net, can you point me to a spot where I could look into "extra 0.15 degrees is in a critical region"

The problem is, I haven't seen the stone. It is on the other side of the continent. It is with a designer whose setting I am in love with. I don't want to settle, any suggestions? Should I be sending it to an appraiser if I do not see it beforehand? They are in in Vancouver, I am in Boston.

Thanks for the help.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,317
The angle is correct.
The angle equates to a deeper depth %.
The depth % is wrong, the reason is there is a tiny culet that has removed 0.2% of the depth %.

I can not make the stone look better. It will look very nice, but it will not be exceptional. If you want to buy it the appraaiser will not be able to make it look better either.
 
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