Find your diamond
Find your jewelry
shape
carat
color
clarity

crown angles on round brilliants

N

novicediamondgirl

Rough_Rock
Joined
Apr 9, 2013
Messages
33
Okay. I am officially confused. When I read the parameters for american ideal cuts --crown angles over 35 and specifically 35.5 degrees are too large. However, on some sites I am seeing stones with these angles and they are calling them ideal cuts. I need to select a stone for a ring and have rejected a stone with the following specs and an now thinking that I am going crazy and I am going round in circles.

Stone:
8.76 x 8.78 5.48
2.58 carats
G, VS1, EX. EX, EX
Table: 56
Crown Angle: 35.5 Crown percentage: 16
Depth: 62.4
pav depth %: 43
pav. angle 40.8
medium faceted-3.5%

any guidance on this?
 
Have you read about the HCA?


You can start with a GIA Ex, and then apply the HCA to it.
https://www.pricescope.com/wiki/diamonds/holloway-cut-advisor
The HCA is a rejection tool. Not a selection tool. It uses 4 data points to make a rudimentary call on how the diamond may perform.
If the diamond passes then you know that you are in the right zone in terms of angles for light performance. Under 2 is a pass. Under 2.5-2.1 is a maybe. Over 2.5 is a no. No score under 2 is better than any other.
Is that enough? Not really.
So what you need is a way to check actual light performance of your actual stone.
That's what an idealscope image does. https://www.pricescope.com/wiki/diamonds/firescope-idealscope
It shows you how and wear your diamond is reflecting light, how well it is going at it, and where you are losing light return. That is why you won't see us recommending Blue Nile or many other vendors, as they do not provide idealscope images for their diamonds. Brian Gavin, James Allen, Whiteflash, Engagement Rings Direct, High Performance Diamonds, and Good Old Gold do.

The Idealscope is the 'selection tool'. Not the HCA.
So yes, with a GIA stone you need the idealscope images. Or you can buy an idealscope yourself and take it in to the jeweler you are working with to check the stones yourself. Or if you have a good return policy (full refund minimum 7 days) then you can buy the idealscope, buy the stone, and do it at home.


Now if you want to skip all that... stick to AGS0 stones and then all you have to do is pick color and clarity and get an Idealscope and you know you have a great performing diamond. Because AGS has already done the checking for you. That's why they trade at a premium. And the idealscope is something that is a 'double' check only. If you REALLY have to you can skip that step with AGS0 stones.


If you want the best cut Super Ideals. I recommend shopping at High Performance Diamonds's Infinity Diamonds, Brian Gavin Diamonds Signature and Blue Lines, and Good Old Gold's Superior and Premium Lines and Whiteflash's ACA and ES lines.

The best thing about all of those I just listed is that all the information you need is posted upfront for you.
 
I would like an E, VS2. close to 2.5 but shy of it because of duties and exchange rate.
so. I am not crazy for not taking it.

I did find this one:

8.60 x 8.64 . 5.29
2.41 E, VS2 3x EX
56 table, 15.5 crown height, 35 crown angle
61.4 depth, 43% pav. and 40.6 pav angle
HCA .8
medium faceted

and

8.8 8.83 5.45
2.59 carat G. VS2
56 table, 15 crown perct. 34.5% crown angle
61.9 % D. 43% pav. depth, 40.8 pav. angle
medium faceted

need to find another alternate....what do you think Gypsy?
 
vendors here do not provide images unless I opt to buy direct on-line which it looks like may be heading in that direction.
 
novicediamondgirl|1394592639|3632211 said:
vendors here do not provide images unless I opt to buy direct on-line which it looks like may be heading in that direction.
Click to expand...


where are you located?
 
novicediamondgirl|1394592541|3632207 said:
I would like an E, VS2. close to 2.5 but shy of it because of duties and exchange rate.
so. I am not crazy for not taking it.

I did find this one:

8.60 x 8.64 . 5.29
2.41 E, VS2 3x EX
56 table, 15.5 crown height, 35 crown angle
61.4 depth, 43% pav. and 40.6 pav angle
HCA .8
medium faceted

and

8.8 8.83 5.45
2.59 carat G. VS2
56 table, 15 crown perct. 34.5% crown angle
61.9 % D. 43% pav. depth, 40.8 pav. angle
medium faceted


need to find another alternate....what do you think Gypsy?
Click to expand...

Run them through the HCA. I'm trying to teach you to be a little self sufficient. =)
 
novicediamondgirl|1394594850|3632234 said:
http://www.jamesallen.com/loose-diamonds/round-cut/2.48-carat-e-color-vs2-clarity-excellent-cut-sku-282521

Okay...so James Allen calls this an ideal and it too has a 35.5 crown angle and 16% crown height?

It looks a lot like the G, VS1 I was looking at.
Click to expand...


Ignore Vendor Labels. They are meaningless. That stone is MUCH deeper than your stone. That's going to get dinged.

Run the numbers through the HCA: https://www.pricescope.com/tools/hca of any stone you are considering. It's a very easy tool. Go ahead, give it a try.

Again, 2 and under is a pass. Under 2.5-2.1 is a maybe. 2.6 and over is a no.

JA offers idealscope images.
 
I am supposing then that the pavillion angle is more critical in this case? or, without an asset it could or could not be good?
 
novicediamondgirl|1394595311|3632237 said:
I am supposing then that the pavillion angle is more critical in this case? or, without an asset it could or could not be good?
Click to expand...

Why are you ignoring me?
 
There is nothing wrong with a 35.5 crown angle as long as the pavilion(both main angles and lower girdle angle/percentage) compliments it and the table is in a range that works with those angles.
The hca will tell you if the mains work with the crown and table then you look for lowers in the 77%+ range as they in general are better with the 35+ crowns and the complimentary pavilion mains. (oec is different and this does not apply to them and you will find exceptions but its a good start)
Some of the most beautiful diamonds I have ever seen have had crown angles well over 35.
They do have a different look than near modern tolk but it can not be considered bad.
 
found the diamond on line in question at jallen and have requested an ideal scope image.
 
novicediamondgirl|1394597155|3632251 said:
found the diamond on line in question at jallen and have requested an ideal scope image.
Click to expand...

DID YOU RUN THE HCA ON IT FIRST?
You have to run the HCA first. Otherwise you are just wasting your idealscope images. As they only allow you 3.
 
Dear Gypsy,

I am sorry that you felt I was ignoring you. I was not...I did run the HCA and it came in at 2.7. But I too have read as Karl just chimed in that the crown angle must be considered in conjunction with the pav. angle.

No one in where I am located gives an ideal scope image. i am working with a very large vendor and they are getting so frustrated with me because I too used the HCA (2.7) and the AGA (1B). They tell me that they only select the best stones---with strict cut standards.

So, further to what Karl has said, does the the pavillion angle on this stone help with the higher crown angle?
 
I have communicated my concerns and they definitely think I am being very anal about these details. Its very frustrating to say the least as I wanted to move forward but cannot.

I have found some alternates but they do not know i they have access to them. My apologies to everyone for being a pain...and I am trying to be self sufficient by using the AGA and the HCA. However, there are instances where I have read that the higher crown angles can still produce a beautiful stone.

Perhaps my problem then is with the vendor and I should just purchase on line directly.

In reference to what Karl said about the 77% ...the lower girdle half facet length on this stone is 80% if that helps.
 
It is your money so you should get what you want.
With an hca of 2.7 if the angles are close to accurate it is not likely the crown and pavilion compliment each other well.
If its the first stone you listed its right on the edge.
Because of the gia badly rounded numbers we can not help much without images with other than educated guesses that may not be hugely accurate with angles that are on the edge.
Its likely not a train wreck but there is better out there.
 
I have another to consider:

Table: 55%, crown percentage: 16% crown angle 35.5%
Depth: 62.6%, Pav. % 43 and pav. angle 40.8
girdle: medium

1B score on aga cut calculator due to crown angles and depth
and depending on what you plug into the HCA using percentages over angles gave me a 1.9

I called GIA too. They said it would be very difficult to find all the parameters I am looking for...and these cuts are all rated EX, EX, EX.
 
lower gridle percentage is 80%
 
GIA rounding makes the numbers close to useless when you get into that range of angles.
 
They seem to like stones with 35.5 crown angles, ask them if they have one with a 40.6 pavilion with the 35.5 and a table of 55-57 listed on the gia report.
That would be a safer choice with no other data.
 
novicediamondgirl|1394647015|3632600 said:
I have another to consider:

Table: 55%, crown percentage: 16% crown angle 35.5%
Depth: 62.6%, Pav. % 43 and pav. angle 40.8
girdle: medium

1B score on aga cut calculator due to crown angles and depth
and depending on what you plug into the HCA using percentages over angles gave me a 1.9

I called GIA too. They said it would be very difficult to find all the parameters I am looking for...and these cuts are all rated EX, EX, EX.
Click to expand...


As Gypsy asked.... Where are you located?

I'm not even in the same realm as these other guys helping you in regards to knowledge. But I would advise listening to them. They know what they are talking about. Especially for a stone of that size? Is something detering you from buying online?

Like they said. It's your money, but if a dealer was getting mad at me, especially with how much your going to she'll out....simply for asking questions. I'd walk. That's crazy.
 
You must log in or register to reply here.
GET 3 FREE HCA RESULTS JOIN THE FORUM. ASK FOR HELP
Jewelry Blog
PriceScope-Concierge-Ad
Find prime cuts.
Top