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Light performance for a 1.15ct round brilliant cut diamond

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
I'm new to the world of diamonds and looking to purchase a 1.15 ct round brilliant cut diamond.

I'm considering the following diamond.

  • Round brilliant
  • 1.15 ct
  • G
  • VS2
  • XXX
  • No flour
Diamond proportions:

diam.PNG

Image:

2diam.PNG

H&A image:

3diam.PNG

My main concern is the 35.5 degree crown angle and how this impacts light performance. From what I've read online, a larger crown angle can result in a dark ring beneath the table. Is this true? Is this effect mitigated due to the larger lower girdle length?

I'm certain that this is not a "hearts and arrows diamond" or "super ideal diamond" but my concern is how far off is the diamond? Is this diamond 90% there? Using the AGSL tables, I know the diamond falls in the range of Ideal.

Should I be concerned about light leakages? Should I be concerned about less light under the table?

Any thoughts would be much appreciated!

Thanks!
 

TODiamonds

Shiny_Rock
Joined
Jul 27, 2019
Messages
260
The stone looks pretty good to me. Yes the crown is steep but the pavilion is complementary. It probably performs fine on the HCA - try running it to see what it spits out. Will there be light leakage? perhaps through an ASET, but nothing your naked eye will notice.

These types of stones can offer great value. With the right combination of angles you can get very close to super-ideal performance without paying 34.5/40.8 super-ideal prices.

Do you have a video?
 
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al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
The stone looks pretty good to me. Yes the crown is steep but the pavilion is complementary. It probably performs fine on the HCA - try running it to see what it spits out. Will there be light leakage? perhaps through an ASET, but nothing your naked eye will notice.

These types of stones can offer great value. With the right combination of angles you can get very close to super-ideal performance without paying 34.5/40.8 super-ideal prices.

Do you have a video?

Thank you so much for your reply!

I do have a video. Please follow this link for the video and GIA report.

https://pck2.azureedge.net/stone-mu...ia.htm?stoneId=2833100052&showMediaType=Video

Al
 

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
The stone looks pretty good to me. Yes the crown is steep but the pavilion is complementary. It probably performs fine on the HCA - try running it to see what it spits out. Will there be light leakage? perhaps through an ASET, but nothing your naked eye will notice.

These types of stones can offer great value. With the right combination of angles you can get very close to super-ideal performance without paying 34.5/40.8 super-ideal prices.

Do you have a video?

I’m getting an HCA score of 1.3 w/

  • Light return: Excellent
  • Fire: Excellent
  • Scintillation: Excellent
  • Spread: Very Good
  • Arrow pointing to BIG
  • Description: Should sparkle beautifully and look a good size for its weight. Confirm with an Ideal-scope, ASET scope or send to an appraise
 

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
Are the comments in GIA reports listed in order of significance?

This one shows additional pinpoints first in the comments. Does that mean the internal graining and surface graining are less significant than the pinpoints. Again, will this affect light performance?

I’m guessing that pinpoints are one of the smallest type of inclusions.

6A2CEB44-73A9-4F64-9DB5-FDCB8F69BAF5.jpeg
 
Last edited:

TODiamonds

Shiny_Rock
Joined
Jul 27, 2019
Messages
260
Overall it looks OK to me.

I wouldn't be concerned about those "Comments" as it relates to your stone. The clarity grade was set based on a crystal - likely the one off to the side just above the girdle which nobody will see anyone. That additional stuff that's not plotted will be negligible.

The only potential concern I have is that the arrows don't look dark and crisp, but that may be more a function of the video platform (JA/BN ones show differently) than the stone.
 

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
Overall it looks OK to me.

I wouldn't be concerned about those "Comments" as it relates to your stone. The clarity grade was set based on a crystal - likely the one off to the side just above the girdle which nobody will see anyone. That additional stuff that's not plotted will be negligible.

The only potential concern I have is that the arrows don't look dark and crisp, but that may be more a function of the video platform (JA/BN ones show differently) than the stone.

Thanks!

I was concerned about the lack of contrast overall and darkness/definition of the arrows as well.

I wonder what the implications are on light performance if the lack of contrast is not due to the video platform and is a characteristic of the physical diamond.

I’ve read that lack of contrast on those facets occur when the pavilion is cut deep. But if this was the case, I would think that the lack of contrast would be even. This diamond shows contrast on some of the facets but not all.

Any thoughts?
 

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
On a side note, is there anyone here that could run this diamond through DiamCalc for me? Looks like the free version is read only.
 

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
Thanks!

I was concerned about the lack of contrast overall and darkness/definition of the arrows as well.

I wonder what the implications are on light performance if the lack of contrast is not due to the video platform and is a characteristic of the physical diamond.

I’ve read that lack of contrast on those facets occur when the pavilion is cut deep. But if this was the case, I would think that the lack of contrast would be even. This diamond shows contrast on some of the facets but not all.

Any thoughts?

Sorry, meant to say arrows not facets in my last paragraph!
 

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
I'm new to the world of diamonds and looking to purchase a 1.15 ct round brilliant cut diamond.

I'm considering the following diamond.

  • Round brilliant
  • 1.15 ct
  • G
  • VS2
  • XXX
  • No flour
Diamond proportions:

diam.PNG

Image:

2diam.PNG

H&A image:

3diam.PNG

My main concern is the 35.5 degree crown angle and how this impacts light performance. From what I've read online, a larger crown angle can result in a dark ring beneath the table. Is this true? Is this effect mitigated due to the larger lower girdle length?

I'm certain that this is not a "hearts and arrows diamond" or "super ideal diamond" but my concern is how far off is the diamond? Is this diamond 90% there? Using the AGSL tables, I know the diamond falls in the range of Ideal.

Should I be concerned about light leakages? Should I be concerned about less light under the table?

Any thoughts would be much appreciated!

Thanks!

Can anyone tell what the actual average lower girdle facet length is on this diamond? Since GIA rounds this number, I was wondering if this particular diamond is between 77.5% and 80% or between 80% and 82.5%?

Any way of knowing?

Thanks for your help, everyone!
 
Last edited:

TODiamonds

Shiny_Rock
Joined
Jul 27, 2019
Messages
260
Can anyone tell what the actual average lower girdle facet length is on this diamond? Since GIA rounds this number, I was wondering if this particular diamond is between 75% and 80% or between 80% and 85%?

Any way of knowing?

Thanks for your help, everyone!

It means it's between 77.5-82.5.

Based on your picture I'd guess it's closer to 80.
 

al_g

Rough_Rock
Joined
Dec 4, 2019
Messages
11
It means it's between 77.5-82.5.

Based on your picture I'd guess it's closer to 80.

Thanks!!!

Sorry, I don't know why I gave those ranges. Too little sleep and not enough caffeine perhaps :)
 
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