AGS0 outside of outline on HCA chart

[JulieN]

link to full report: http://www.jamesallen.com/certs/5000460CER.JPG

so, what''s the dealio?

 

[Carlotta]

Looking forward to hearing the experts chime in!!!! (where was it that it was noted when a crown angle is over 35 - was that on GIA cert????)

Anyway, I will look forward to hearing from the experts on this.....(especially after all of the "concern" [bashing] of GIA certs, etc....)

 

[belle]

hca works with a given set of angles to estimate potential candidates for ags0 and gia excellent. it does not take into account minor facets and optical symmetry which can effect face up appearance. since this stone is borderline angle wise and ags grades face up appearance, it must have proved to be a good performer and earned the top grade.

 

[Mara]

HCA likes more mass-acceptable ideal numbers, particularly angles, for stones to get it's under 2 grade typically. The crown angle on this one is most likely pushing it out of the HCA under 2 range. Some might like a stone like that, but I wouldn't buy it. I'm too picky. Just because it's lisetd AGS0 doesn't mean it's a great stone to me.

That stone as listed gets a 3.5 on the HCA but if you just change the crown angle and nothing else, a 35 crown angle gives it a 2 and a 34.7 crown angle gives it a 1.8. This is why we often tell people to not use HCA as a gospel, because there are stones out there that are above 2 that are going to be really beautiful. I have my own mental set of parameters for stones that will typically get under 2 on the HCA so it covers 'all bases'.

 

[JulieN]

ah, yes, minor facets