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Do high crown angles affect a stones scintilation & fire

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Taz

Rough_Rock
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Mar 17, 2007
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Do high crown angles affect a round diamonds brilliance and scintillation? Most everything I have read says they do. I am torn between 2 diamonds. Both stones are nice however I need to pick one. Both their proportions are within the ideal cut range except that the 1.28 GIA FVS1 stone has high crown angles. I was told that this knocked the stone down from an excellent to a Very Good rating.



One diamond is an ideal cut AGS000 FVS2 1.14 for 9500.00. The other is an ideal cut GIA all Very Goods on the cert, FVS1 1.28 (this is the stone with the high crown angles) for 10,500.00.



I compared both stones side by side on my bare hand in the store, under regular lighting not the usual bright store lights. The AGS 1.14 stone seemed a bit better with more white brilliance and sparkle. When I compared the stones on my hand by the window(in a more natural outside light) the other GIA 1.28 stone seemed to stand out a bit more showing more spectral sparkle than the AGS 1.14 stone (which only seemed to show a white sparkle, no spectral colors) when I moved my hand. The store told me because of the higher crown angles on the 1.28 stone it would show more scintillation outside than inside. I thought a good ideal cut diamond was supposed to sparkle, have fire and scintillation in both types of light or was I just comparing them wrong and missing the spectral light on the AGS 1.14 stone? I want to purchase and ideal diamond and I do like the size of the 1.28 however, I want to purchase the better quality diamond. The high crown angles concern me



I know a lot is personal preference but would you please let me know which stone you think is the better deal?

 

Cehrabehra

Super_Ideal_Rock
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strmrdr

Super_Ideal_Rock
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it depends on the pavilion angle in relation to the crown angle.
If its lowered to a VG then its likely not a good match get the numbers from the cert.
Which ideal range?
There is no longer a range for AGS ideal its a stone by stone basis.
 

Cehrabehra

Super_Ideal_Rock
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Date: 3/18/2007 2:39:11 AM
Author: strmrdr
it depends on the pavilion angle in relation to the crown angle.
If its lowered to a VG then its likely not a good match get the numbers from the cert.
Which ideal range?
There is no longer a range for AGS ideal its a stone by stone basis.
VG in GIA might not be a bad stone though... the AGS stone is the one he is saying is very bright with a lot of white... the gia stone has more fire and personally I''d take fire over white light return any way - but the white return can be flashier if you want to cause a stir from across the room. What might not be an ideal match to GIA could be an *awesome* match if you like fire.

Again, I''d use your eyes!!

And yes, some stones are better at white light and others at color... my ring diamond is amazing at color and probably average for white.... my earrings on the other hand are EXTREMELY white bright but have almost no color - you have to hold it next to a christmas tree and then *squint* LOL My earrings have a very shallow crown and my ring stone has a very high crown.
 

Taz

Rough_Rock
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Mar 17, 2007
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Thanks for all your great info... I have a second appt tomorrow morning at the jewelers to look at the stones again together. I am going to purchase one of the stones.

I agee by GIA knocking down the cert to a Very Good I was concerned. The diamond buyer was nice, she said it was a personal preference regarding higher crown angles and not the industry norm. I did ask an apprentice jewler at the store for his opinion. He picked the AGS000 1.14 stone when both diamonds were face up together on my hand, like me. He said the higher crown angles were throwing him off. Then when he took a second look at both of stones in a brighter light he picked the GIA 1.28, it scintilated more. I guess this is what you all mean by fire. Thanks for reassuring me that some diamonds do only show white light and some will have spectral light also. I thought I was nuts in the store. I never thought 2 diamonds would look so different in 2 types of light.

Thank goodness I only have to make this choice once.
 

Taz

Rough_Rock
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Mar 17, 2007
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I do not know the ideal range just the table, depth and diameter I noted earlier. Where is the pavilion and crown angles noted on the GIA certificate? I did not see them. I will look for them tomorrow when I am at the store. What should they be or what range should they be?
 

Ellen

Super_Ideal_Rock
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Jan 13, 2006
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Date: 3/18/2007 6:40:19 PM
Author: Taz
I do not know the ideal range just the table, depth and diameter I noted earlier. Where is the pavilion and crown angles noted on the GIA certificate? I did not see them. I will look for them tomorrow when I am at the store. What should they be or what range should they be?
Hi Taz,

I''m giving you the link to a GIA stone. In the middle towards the bottom is a diagram of the diamond. The numbers on the right side of it, next to the crown and pavillion are it''s angles. (34.5 and 40.8)

http://204.17.89.15/show.php?image=2883/gia.jpg
 

He Scores

Shiny_Rock
Joined
Mar 26, 2005
Messages
230
If both diamonds have similar D/S ratios and similar table sizes, then the GIA stone will have a flatter bottom angle rendering less brilliance. The brilliance generator of a diamond is the bottom angles. All the bottom angles, not the averages of the bottom angles.

Talk about GI/GO.


Bill Bray
Diamond Cutter
 

Modified Brilliant

Brilliant_Rock
Trade
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Mar 24, 2005
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Date: 3/19/2007 2:20:48 AM
Author: Taz
What is GI/GO mean?
Garbage In, Garbage Out (abbreviated to GIGO) is an aphorism in the field of computer science. It refers to the fact that computers, unlike humans, will unquestioningly process the most nonsensical of input data and produce nonsensical output. It was most popular in the early days of computing, but has fallen out of use as programs have become more sophisticated and now usually have checks built in to reject improper input. The aphorism GIGO was originally coined by Stephen "Wilf" Hey, a programmer who had a regular column in PC Plus magazine.

from Wikipedia.

www.metrojewelryappraisers.com
 

strmrdr

Super_Ideal_Rock
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23,295
What Bill is saying is that we dont have enough info.
The numbers from the cert dont have all the answers but atleast it will give us an idea of what your dealing with.
 

strmrdr

Super_Ideal_Rock
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Date: 3/18/2007 12:40:34 PM
Author: Cehrabehra


Date: 3/18/2007 2:39:11 AM
Author: strmrdr
it depends on the pavilion angle in relation to the crown angle.
If its lowered to a VG then its likely not a good match get the numbers from the cert.
Which ideal range?
There is no longer a range for AGS ideal its a stone by stone basis.
VG in GIA might not be a bad stone though... the AGS stone is the one he is saying is very bright with a lot of white... the gia stone has more fire and personally I'd take fire over white light return any way - but the white return can be flashier if you want to cause a stir from across the room. What might not be an ideal match to GIA could be an *awesome* match if you like fire.
A stone can have nice fire and still be a dud in other lighting conditions.
A reasonable balance of white light return and fire will almost always make for a stone that looks better in more conditions.
Now within that reasonable balance zone there is a whole lot of room for preference in fire over brightness or brightness over fire.
Millions of people buy badly cut diamonds using their eyes every day.
Once its established that a person is dealing with well cut stones then yea use your eyes but get a baseline first otherwise you may be looking at a cwappy diamond and comparing it too a slightly less cwappy but still cwappy diamond.

GIA EX is wide enough that very few decent combos will get VG.
 

Taz

Rough_Rock
Joined
Mar 17, 2007
Messages
15
Hi - I found out the Crown & Pavilion Anges what do you think?

The GIA 1.28 diamond is
FVS1
Table - 57
Crown Angle 37 degrees
Pavilion Angle - 40.2 degrees
Cutlet - none

The higher crown angles were throwing me off when I compared it to the other diamond which was a AGS000 1.14 diamond on my hand. I inputed the numbers on the holloway cut advisor and they came back a 1.5 excellent for fire.
 

Cehrabehra

Super_Ideal_Rock
Joined
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Messages
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Date: 3/19/2007 2:53:26 PM
Author: Taz
Hi - I found out the Crown & Pavilion Anges what do you think?

The GIA 1.28 diamond is
FVS1
Table - 57
Crown Angle 37 degrees
Pavilion Angle - 40.2 degrees
Cutlet - none

The higher crown angles were throwing me off when I compared it to the other diamond which was a AGS000 1.14 diamond on my hand. I inputed the numbers on the holloway cut advisor and they came back a 1.5 excellent for fire.
too funny... that is in AGS range but not GIA range! Ha! You found a rare FIC and that 37 crown angle is amazing!

If you''ve seen this stone and you like this stone I would BUY this stone. I would, in this case, not be turned off by the GIA VG rating. This stone is a bit outside the box and you may sacrifice some brilliance or white brightness for colored fire but IMO um no brainer!!! fire rules!!!!
 

strmrdr

Super_Ideal_Rock
Joined
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Messages
23,295
if you like fire thats a good one.
And one of the exceptions.
You will be giving up some white light return but not a huge amount.
 

Cehrabehra

Super_Ideal_Rock
Joined
Jun 29, 2006
Messages
11,071
Date: 3/19/2007 3:17:28 PM
Author: strmrdr
if you like fire thats a good one.
And one of the exceptions.
You will be giving up some white light return but not a huge amount.
ditto - and it goes to show that AGS is more about angle interaction than just having limits for limits'' sake.
 

Taz

Rough_Rock
Joined
Mar 17, 2007
Messages
15
Thanks! for everyone assistance! I bought the GIA stone. What does FIC & IMO mean?
 
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