When we are evaluating a diamond the colour, clarity and carat are determined for us by the nature, the only part that can be influenced by human beings is the cut itself.
The cut of diamonds is one of the most important characteristics of the diamond as a well-cut diamond or a badly cut one in the same category can make a huge difference in price. A stone of higher quality and worse cut is usually less desirable than a stone with better cut and lower quality. A diamond can also be polished in different shapes, this is usually done when the rough diamond has an irregular shape and the loss of weight for polishing a round diamonds is not economically feasible.
Diamonds were first found in the Golconda region in India about 4500 years ago. These stones were praised for their hardness and luster. They were used only in their rough form for about 4000 years. In the 14th century diamond polishing was invented. The first improvements man made to diamonds was to polish the rough to a perfect octahedral shape. The second step was to cut a table on the octahedral, this was called the table cut and was done during the 15th century, during that time the polishers started to understand the importance of a culet and the table cut evolved to the old single cut. In these cuts the diamond would not shine as the modern cuts do and as such they were not as popular as other gemstones. In the 17th century the first brilliant cut, the Peruzzi cut was invented, Peruzzi cut diamonds still didn’t have a ‘life’ as vivid as modern cuts, but they did have much more brilliance than the old single cut. In the 18th century the old mine cut was developed and later came the old European cut, the real predecessor of the modern brilliant cut. In 1919 Marcel Tolkowsky calculated the perfect proportions for the maximum brilliance and developed the Tolkowsky cut. Since then by using computer models the perfect proportions are being continuously researched and in the last 30 years, we have seen further improvement in polishing of diamonds to increase the brilliance.
These and more parameters are being checked and graded. Symmetry as well as Proportions is a cumulative grade, which means if for example the culet is not centered and receives a Fair grade, but all the other parameters are excellent the symmetry will still receive a Fair result.