Star Length Percentage

[jolar]

How important is star length percentage?
From what I''ve read I''m getting the impression more is better due to more light return?
Such as this diamond I''m considering would be possibly low on star length percentage?

TIFFANY GEMOLOGICAL LABORATORY REPORT

25042905/J10150437
DIAMOND REGISTRATION NUMBER

SHAPE ROUND

CUT BRILLIANT

MEASUREMENTS 6.48 - 6.51 x 4.04 mm
MINIMUM GIRDLE DIAMETER - MAXIMUM GIRDLE DIAMETER x DEPTH IN MM
CARAT WEIGHT 1.05 CARATS

COLOR GRADE F

FLUORESCENCE NONE

PRESENCE

PRECISION OF CUT EXCELLENT

SYMMETRY EXCELLENT

POLISH VERY GOOD

CLARITY GRADE VS1

ENHANCEMENTS (BESIDES CUT/POLISHING) NONE

CUT PROPORTIONS

TOTAL DEPTH PERCENTAGE 62.2% PAVILION ANGLE 40.6°

TABLE SIZE PERCENTAGE 55% LOWER HALF LENGTH PERCENTAGE 80%

CROWN HEIGHT PERCENTAGE 16.2% GIRDLE THICKNESS MEDIUM TO SLIGHTLY THICK

CROWN ANGLE 35.5° GIRDLE FINISH FACETED

STAR LENGTH PERCENTAGE 50% CULET NONE

PAVILION DEPTH PERCENTAGE 42.6%

CROWN INSCRIPTION T&CO.J10150437

GIRDLE INSCRIPTION NONE

 

[stone-cold11]

No, should be just fine.

 

[rockabee]

here is a good recent thread

https://www.pricescope.com/community/threads/can-someone-please-explain-what-stars-do.129521/

and good old gold has a great tutorial as well. links are in the thread.

 

[Lorelei]

Date: 11/18/2009 9:16:39 PM
Author: rockabee
here is a good recent thread

https://www.pricescope.com/community/threads/can-someone-please-explain-what-stars-do.129521/

and good old gold has a great tutorial as well. links are in the thread.

Thanks for referring that rockabee, it should help the OP.

Jolar your stars are fine.

 

[jolar]

Thanks guys

 

[FB.]

Bear in mind that GIA round-off star and lower half to the nearest 5%.

The most common star proportion seems to be 50%. Next most common is 55%.
Stars of 45% or 60% are not very common, but there are a few.

Likewise. the most common lower half proportion seems to be 80%. Next most common is 75%.
Lower half of 70% or 85% are only occasionally seen.

 

[John P]

Date: 11/19/2009 6:31:43 AM
Author: FB.
Bear in mind that GIA round-off star and lower half to the nearest 5%.

The most common star proportion seems to be 50%. Next most common is 55%.
Stars of 45% or 60% are not very common, but there are a few.

Likewise. the most common lower half proportion seems to be 80%. Next most common is 75%.
Lower half of 70% or 85% are only occasionally seen.

85% is frequent in diamonds produced pre-2006 and still appears with frequency in commercial markets. This can give a facelift under direct spotlighting.

 

[jolar]

Date: 11/19/2009 9:24:21 AM
Author: John Pollard

Date: 11/19/2009 6:31:43 AM

Author: FB.

Bear in mind that GIA round-off star and lower half to the nearest 5%.


The most common star proportion seems to be 50%. Next most common is 55%.

Stars of 45% or 60% are not very common, but there are a few.


Likewise. the most common lower half proportion seems to be 80%. Next most common is 75%.

Lower half of 70% or 85% are only occasionally seen.

85% is frequent in diamonds produced pre-2006 and still appears with frequency in commercial markets. This can give a facelift under direct spotlighting.

Does this make the diamond appear brighter?
Yeah, newbie. *eyes left* post count

 

[Laila619]

I still don't quite get stars and I started the other topic on them! It seems like bigger stars are a good thing to have, but no one recommends stars at 60 for example.

 

[John P]

Date: 11/19/2009 4:05:08 PM
Author: jolar

Date: 11/19/2009 9:24:21 AM
Author: John Pollard

85% is frequent in diamonds produced pre-2006 and still appears with frequency in commercial markets. This can give a facelift under direct spotlighting.

Does this make the diamond appear brighter?
Yeah, newbie. *eyes left* post count

In a way: Narrow pavilion mains return light with more intensity in bright spotlighting. But too narrow and the diamond is not as appealing in normal or soft lighting.

Date: 11/19/2009 4:09:56 PM
Author: Laila619
I still don''t quite get stars and I started the other topic on them! It seems like bigger stars are a good thing to have, but no one recommends stars at 60 for example.

Remember the give-and-take. When you adjust the stars it changes the relative angle of the upper girdle facets. Too long or short and you risk reduction in performance along the edge of the diamond.

 

[Laila619]

John,

So is there a rough formula as to what stars are too long or too short? Do the stars and LGF have the same relationship as the crown and pavilion angle? In other words, if one is bigger, the other should be smaller? Thanks

 

[John P]

Date: 11/19/2009 4:30:33 PM
Author: Laila619
John,

So is there a rough formula as to what stars are too long or too short? Do the stars and LGF have the same relationship as the crown and pavilion angle? In other words, if one is bigger, the other should be smaller? Thanks

In conventional RBs the stars have the least influence on performance but can subtly fine tune some qualities. "Safe range" is 45-65% with some borderline exceptions, but it depends on entire configuration.

While the stars work to some degree with lower halves - as you infer - they are stepchildren to the mighty pavilion/crown and table/lower half relationships. Then you have those testy upper girdles, subject to painting or digging by an evil brillianteerer, who also determines the angle/length of the stars; they go on last in the process.