Blue Nile Signature Ideal-cut vs. Tiffany's Excellence Cut - are they the same?

[ame]

My pleasure

 

[ame]

Someone commented that a good cut has 57/58 facets.

A standard Round Brilliant diamond has 57/58. Regardless of how well cut it is. Cut quality is based on angles and facet interplay.

 

[akimoto]

And angles can be measured with the HCA calculator as a guide?

 

[ame]

No, a general idea of cut quality can be gotten from HCA. The Angles themselves are measured by a reputable lab and on the grading report.