Additional Diamond Features
People generally tend to follow the 'four Cs' of carat weight, cut, clarity and colour when researching diamonds to buy, but there are other features that can greatly affect a diamond's appearance and quality – some of which are considered when diamonds are professionally graded.
Symmetry
We recommended you purchase a diamond with either good or excellent symmetry, as this can have marked effects on its value and shine – especially in diamonds with excellent clarity. As magnifying equipment is needed to accurately appraise a diamond's symmetry, you should check a diamond's certificate for its symmetry attributes instead of trying to make a judgement through the naked eye. Symmetry is generally graded based on how many facets a diamond has and their shape, as well as the positioning of the table and culet, and shape of the girdle. Problems with symmetry are generally less noticeable in diamonds with low clarity.
Depth Percentage
The depth percentage of a diamond is calculated by dividing its depth (the length from the table to the culet) by its widest diameter. This is important because a low depth percentage can alter a diamond's brilliance and shine, as well as having other influences on its overall appearance. The diamond industry considers the ideal depth percentage to fall between 58% and 60%.
Table Percentage
The table percentage of a diamond measures the table width (the flat area at the top of the stone) against the diamond's diameter at its widest point, and can significantly influence the diamond's brilliance and fire properties. An ideal table percentage for a round brilliant diamond is considered to be around 53%, while emerald, princess and radiant cuts fall closer to 75–80%. Round diamonds require a large table surface to optimally reflect light; therefore, such diamonds tend to be of higher value than diamonds of the same carat size with a smaller table.
Fluorescence
Some white diamonds will illuminate with a bluish or purplish tinge when held under UV light. This is very common and most diamonds will contain some fluorescence, with medium to lower levels almost undetectable by the naked eye. A diamond with a strong or higher fluorescence may look murky or cloudy in regular light, while, if their colour grade is H or below, it may actually improve their appearance as it can balance out their slight yellowish tinge.
Polish
The quality of a diamond's polish won't generally affect its value, but it can have significant impacts on how it reflects light, which is what gives diamonds their brilliance and shine. Diamonds that are poorly polished appear full and cloudy; therefore, it's important to choose a diamond that has been thoroughly polished before purchasing it.
