Just when do we say that a diamond has a brilliant cut?

Is it with how far one can view the diamond with his naked eye? If so, then what is the distance one must be able to see the diamond from to qualify it as a brilliant cut diamond. Or is it with the symmetry and smoothness aspect? If so, how then can one determine the required polish and symmetry aspect of it? How about the people who make the standards? Do we follow the AGA standards? Or do we use the HCA and AGS guidelines? Or the GIA, which made a comprehensive study of 20,000 proportions with 70,000 observations of 2,000 diamonds?

One should also think, what is it with the brilliant cut that people are debating about? How would it be advantageous if one has a brilliantly cut diamond? Is it the beauty? Is it the money value?

So when does a diamond achieve a brilliant cut? Or more specifically, how does one define a brilliant cut diamond?
Brilliance is the amount of light allowed to enter a stone and how the angles cut into the stone reflect the light back to the naked eye. Brilliance encompasses the behavior of light when it is reflected or refracted at junctions between the aspects it is traveling through. With these factors, the optimum angles between facets will be influenced, thus affecting the brilliance of the diamond. The depth and the proportion of the crown to the pavilion are being seen.

A brilliant cut diamond is any diamond that is cut to a standard of 58 facets or 57 if the culet is excluded, that reflect light. Thirty three (33) facets are on the crown and twenty five (25) facets are on the pavilion, or bottom half of the stone. Although in the early years, the Mazarins, the first brilliants known, had only 17 faces on the crown and Peruzzi had 33 on it, nonetheless, they are considered the primers in Brilliant cut diamonds and have become part of the history.

With the evolution of the brilliant cut diamond, several variations have existed along the way. Notably, the oval, pear, and marquise cuts have a share of market in the industry.