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Additional Qualities

Additional Qualities

As well as the 4Cs, GIA also consider other attributes when grading a diamond including fluorescence, polish and symmetry, the details of which will all be shown on your GIA certificate. Below is an overview of each quality and the effect they have on a diamond - and you can see GIA's Anatomy of a Diamond for more detail on the phrases used below.



Fluorescence

Fluorescence25 – 35% of diamonds emit a visible light when exposed to UV rays, this is referred to as fluorescence.

For many people, the presence of fluorescence doesn’t majorly affect the colour of a diamond as much as other factors do – including the cut, so the preference to buy a diamond with fluorescence is a purely personal one.

In some instances a diamond that has medium to strong fluorescence can improve the appearance of a slightly yellow coloured diamond, as the most common visible colour emitted from fluorescence is blue, which in a yellowish diamond can make it look white or colourless. Blue and yellow are colour opposites and tend to cancel each other out, so blue fluorescence masks the yellow colour. However, a small percentage (around 5-10%) of diamonds with fluorescence emit other colours including yellow or green.

A diamond that fluoresces has the same integrity as one with no reaction to UV – there is no weakness or structural defect in either stone.

Each GIA report will measure the strength of the diamond’s reaction to UV, which is then presented as a measurement from Very Strong to None.

Polish

PolishAlthough diamonds are the hardest material known, it still has different degrees of hardness in different directions, which makes it even more difficult to cut.

As the machinery cuts through the rough diamond, it leaves polishing lines as a result of the resistance. These polishing lines are then removed by craftsman polishing the diamond on a wheel.

Because the hardness of the diamond varies with direction, the polishing of each facet has to be done by changing the direction each time. Although the goal is to remove all the polish lines, it is absolutely vital to be careful to not to over polish the stone as the surface can easily get burnt and leave a 'lizard skin' pattern on the surface, making the stone useless.

The craftsmen use experience, patience and persistence to strike the perfect balance of achieving the flawless surface on each facet whilst stopping any burn or damage. Any polish marks left in the stone will refract the light, causing brilliance and fire to reduce and if the polishing lines are numerous, they can make the diamond look less transparent and affect its sharpness.

GIA will grade a diamond's polish from Excellent to Poor.

Symmetry

SymmetrySymmetry is the perfect alignment of all the facets on a diamond, meaning the bottom facets connect with the top ones perfectly, and the facets on the right side are mirror images of the facets of the left side depending on the shape of the diamond.

This perfect arrangement directly relates to how each section is reflecting the light and ultimately the brilliance of the complete stone.

A diamond cut with perfect symmetry will have relative facets cut in a way to display same width, same length, same sharpness, same angles at intersections and even the height is uniform throughout so that no matter which angle the stone is looked at it will reflect the light uniformly without any black patches and giving out maximum sparkle.

GIA reports will grade each diamond's symmmetry on a scale from Excellent to Poor.