star/upper ratio and its relation to cut?

[computerguy]

I'm looking at a sarin scan from the EGL people. It is not the EGL cert itself. Anyways, on the sarin scan there are the words: "star/upper ratio: 53:47".

What does that mean? I've read a more than a few pricescope posts about cut and cut parameters, but I haven't come across this one (yet). I presume that this is concerning the star shaped pattern of facet intersections on the underside of the stone in comparison to the upper part of the stone. But the question remains..."so what"?I'm looking at a sarin scan from the EGL people. It is not the EGL cert itself. Anyways, on the sarin scan there are the words: "star/upper ratio: 53:47".

What does that mean? I've read a more than a few pricescope posts about cut and cut parameters, but I haven't come across this one (yet). I presume that this is concerning the star shaped pattern of facet intersections on the underside of the stone in comparison to the upper part of the stone. But the question remains..."so what"?


Sorry for the crappy formatting. I hit some control key and it wonked out.

Oh, yeah, this is a round brilliant cut.
RWW

 

[resilient]

GOG's website mentioned something about the star, upper girdle and lower girdle facets, and their effects on a diamond. You can view it at the link below.

http://www.goodoldgold.com/minor_facets.htm

 

[computerguy]

I went to the GOG website and had a gander. It's apparent that the words "star/upper ratio: 53:47" are not too informative and more sarin data is needed to make a better comment on visual performance (according to the GOG web page).

Can one make any sort of comment based on the words "star/upper ratio: 53:47"?
RWW

P.S.: This stone is an AGS 000 stone, H&A, etc. I just sent it in to EGL to get the additional sarin data.

 

[DiamondExpert]

The star/upper ratio just tells you the length of the star facets. For example, when you measure the distance from the edge of the table through the center of the star facet to and through the point where the upper girdle facets meet to the edge of the girdle (see poorly drawn red lines on one of Rhino's figures) you get the relative proportion of that distance occupied by the star and the upper girdles...naturally, the two figures add up to 100 if you express the ratio as % of that distance occupied by each.

 

[computerguy]

Gary,

Thanks for the explanation. Is the star/upper girdle ratio in the sarin report of any use without any additional angle info on the star, upper girdle and lower girdle facets?
RWW