While there is a largte amount of information on the internet and in books about the cut, clarity, colour and carat of a diamond (the 4C’s respectively), there is little information on the method used for cutting and polishing a diamond.
The cutting process begins when a rough diamond is cleaned and then a cut is estimated. Cut is estimated now by computer software, which determines the desired proportions depending on a performance parameter. In this way most, if not all polishing companies, could cut an ideal diamond, but this is not always possible and not always desired. For example, you may not be able to afford a excellent cut at your desired carat weight and so there is variation is common.
After the proportions have been estimated and confirmed, the rough diamond is cut to it’s desired shape, usually round brilliant but there are a number of different shapes (called fancy cuts) that can also be cut. Common methods of cutting are a saw blade with diamond dust on it or laser cutting. Later on after some polishing, the diamonds are also cut against each other (two diamonds are spun in contact).
Polishing involves not only removes some weight from the diamond but it also allows more light to enter the diamond; this helps grading but also helps give the it’s characterists dispersion and refraction values. Firstly eight facets are polished onto the pavillion (the bottom side of the diamond), before a cleaning and quality control check. Then eight more are polished on the crown (top sides of the diamond) before more quality control and further polishing. Fifty-eight facets are eventually polished into the top and bottom of the diamond (this is a cumulative number). Other facets that are excluded from the total count are most common the girdle (the part that seperates the top of the diamond from the bottom), and sometimes on the table to cover imperfections that occur when polishing. Once this is completed you have completed a diamond cut.
The exact angle of the facets differ depending on the standard, in America this is the American Standard (also known as the Tolkowsky Brilliant), while in Europe it is the Practical Fine Cut. Although the angle arrangement is slightly different they are essentially the same apperance, so similiar there would be no visible difference.