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Crown and Pavilion Angles?

I

Iamme

Rough_Rock
Joined
Feb 9, 2014
Messages
15
Hello all - First let me say thanks! I have learned a great deal through this forum about diamonds! More than I ever thought given what I was hearing in the stores.

One thing I'm still not sure about is crown and pavilion angles. I know they're important but I've read that it's okay to be lenient on the crown angle, then i read somewhere else it's much more important than the pavilion. My head is spinning!

I've come to the conclusion that the perfect combination seems to be 34.5/40.8... but how much leniency is there? For example, would a 33/40.8 be acceptable? or say a 34/41.5?

Thanks!
 
I assume you aren't talking about AGS0 stones. So for GIA Ex stones I just use the HCA as a short cut.

https://www.pricescope.com/tools/hca

Anything under 2 is fine. Anything 2-2.5 is a maybe. Get an idealscope in either case. Anything above 2.5 is a fail. You don't use it on AGS0.
 
Yes - I was talking about GIA Stones... I had read that if it's an AGS0 stone, I don't have to worry about the angles, etc since AGS0 is as good as it gets...

I also read that HCA is a rejection tool and not a selection tool.. so even if it gets below 2, it could still be no good?

Sorry for my ignorance, this is just all so overwhelming and I want to get the best possible stone for my girl :)
 
It absolutely is a rejection tool. The idealscope image is the selection tool. But since you can't run around idealscoping everything in sight. You use the HCA to narrow the field to a few contenders that have a good chance of having a good idealscope. THEN you ask for the idealscope image of the stones. And pick among them.

I must have miss typed above. Sorry for the confusion:

2 and UNDER is a pass. 2.5 and UNDER to 2.1 is a maybe. 2.6 and OVER is a fail. It's pass fail. No score 2 and under is better than another.

And yes, AGS0 has been screened for light perfomance. Though having an idealscope in addition is nice. But not strictly necessary.
 
Okay so if it's under 2 on HCA, I won't worry about the crown/pavilion angles then.

I found a RB that scored 0.7 on HCA on Blue Nile for a price I'm comfortable (and haven't been able to find better elsewhere, including PS vendors) with. Since Blue Nile doesn't provide IdealScopes, my plan is to buy the diamond and take it to a 3rd party appraiser (charging $75) to do an analysis including using an ASET scope.

I was very worried about the stats and finding a good match... do you all think this plan would work? I'm trying not to have to return diamonds since I have to pay return shipping/insurance but no other vendor has a better price!
 
Iamme|1392852612|3618893 said:
Okay so if it's under 2 on HCA, I won't worry about the crown/pavilion angles then.

I found a RB that scored 0.7 on HCA on Blue Nile for a price I'm comfortable (and haven't been able to find better elsewhere, including PS vendors) with. Since Blue Nile doesn't provide IdealScopes, my plan is to buy the diamond and take it to a 3rd party appraiser (charging $75) to do an analysis including using an ASET scope.

I was very worried about the stats and finding a good match... do you all think this plan would work? I'm trying not to have to return diamonds since I have to pay return shipping/insurance but no other vendor has a better price!
Click to expand...


You can ask Wink at High Performance Diamonds if he can get that stone in for you, and beat the price. And he can provide you with an idealscope image.


At Blue Nile you have to pay return shipping? Huh. I didn't know that. At JA you don't. Interesting.
 
I stick with

crown angle: 34.0-35.0

pavilion angle: 40.6-41.0

table: 54-57 (or 58)

depth: 60-62.3

These measurements generally result in stones that fall into ideal cut territory, and therefore, a good HCA score.
 
Iamme|1392849558|3618861 said:
Yes - I was talking about GIA Stones... I had read that if it's an AGS0 stone, I don't have to worry about the angles, etc since AGS0 is as good as it gets...

I also read that HCA is a rejection tool and not a selection tool.. so even if it gets below 2, it could still be no good?

Sorry for my ignorance, this is just all so overwhelming and I want to get the best possible stone for my girl :)
Click to expand...

AGS 0 may be as good as the grading gets, and it is good, but I have consistently found that if you put two, three or more AGS 0 diamonds on a tray and show them around, there is almost always one that is chosen as the prettiest most often in that group of diamonds.

Even with AGS 0s there is going to be those at the very tippy top of the grade and the hangers on that just barely made it. You may not be able to tell on the paper, but the eyes can see what the eyes can see.

Wink
 
Gypsy said:
You can ask Wink at High Performance Diamonds if he can get that stone in for you, and beat the price. And he can provide you with an idealscope image.
Click to expand...

I already put the diamond on hold at Blue Nile... a local jeweler found the same diamond and told me that when he called the broker, he said the diamond was already sold. I assume the same would happen with Wink? :( I guess my own eagerness is going to prevent me from getting an Idealscope image.

Gypsy said:
At Blue Nile you have to pay return shipping? Huh. I didn't know that. At JA you don't. Interesting.
Click to expand...

Yeah Blue Nile asks that you pay for return shipping and insurance, I think it goes to Seattle. The cost isn't overly high but I wouldn't want to be sending a bunch of diamonds back!

diamondseeker2006 said:
I stick with
crown angle: 34.0-35.0
pavilion angle: 40.6-41.0
table: 54-57 (or 58)
depth: 60-62.3
These measurements generally result in stones that fall into ideal cut territory, and therefore, a good HCA score.
Click to expand...

Those are the same measurements I see in a lot of places, but they really are pretty tight and a lot of stones fall out of that range (to me) just a little... that ties back to my original question about how much leniency there really is. Good example was the 33/40.8 and/or the 34/41.5. Both of these seem to score well on HCA but fall out of the ideal range mentioned?
 
The specs Diamondseeker gave you are for those starting their search, to make things easy for them by giving them a 'sure fire' set of specs that will pass the HCA. But they are very restrictive. And ask long as you get a good HCA and a good idealscope there are a TON of diamonds outside of those ranges that will give you ideal light performance and a GORGEOUS diamond.

Many AGS0's don't fall into that range. For example.

So you don't need to stick to those ranges. But they are helpful for those who want a guide to stones that will pass the HCA each time, when they are searching. But as long as you have a good idealscope image to verify light performance you are fine.
 
Yes, I mainly use those parameters for stones that don't have images already provided. I never search for my own diamonds at vendors who don't provide all that on the site. though. For people who can order multiple stones at one time, they can order ideal cut stones with different measurements to see what they prefer. For those who don't have that luxury, I recommend sticking to the narrow parameters. But I will say, the perfect hearts and arrows stone that I had was t:56, depth: 61.?, ca: 34.5, pa 40.8, so I found that those parameters resulted in an outstanding stone.
 
I have an AGS 0 that's 35.7 & 40.6 and is a sparkling fireball.
The guidelines listed before are very good ones to follow, but there are some angles on either side of that range that can offset each other (like a shallower pavillion/steeper crown) and still make for amazing light performance. You can't get too radical, though.
 
Wow, buying diamonds is tough!

I think I get it now, essentially there are lots of beautiful diamonds out there and the numbers that everyone has posted is as close to a "sure-fire" way to get a good diamond even though there are lots of other combinations out there. Based on this, I'm going to give the diamond on Blue Nile a shot and hope for the best from the appraisal...

The diamond I'm going to pick up and take to the appraiser:
Table 55%
Crown: 33 degrees
Pavilion: 40.8 degrees
Depth: 61%
Girdle: 3.5%
HCA: 0.7

I'll take it to Carole Richbourg (found here on PS, in the appraiser's list) http://www.finejewelryappraiser.com/

Please stop me if the diamond has issues you can see!
THANKS!
 
Just thought I'd post an update on the diamond I picked up.. I took it to the appraiser this afternoon and she said it was a great cut. When she looked using the ASET scope, she said that it looked close to an AGS0 cut with very little leakage. She showed me both ASET and Idealscope and both looked great!

I guess there really is a bit of leniency on these numbers.

THANKS again for all the advice!!!
 
sounds good. congrats.
 
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