The nature of diamonds is such that even a very SMALL variation in any of the 4 C’s will have a significant effect on value. To give you an idea of just how sensitive the value of a diamond is to each characteristic, here are some examples (assuming all other characteristics remain constant):
Carat: a difference of 0.1 of a carat (or 0.02 grams) can affect the value of a diamond by as much as 70%.
Colour: a diamond’s colour ranges from D to Z. However the “white” colour range is from D to I (D, E, F, G, H, I). The difference between each colour is very subtle; however a D colour diamond is around 200% more valuable than an I colour diamond. The difference between a D colour diamond and an E colour diamond(which is almost impossible to tell without a set of diamond master stones) can be as much as 40%.
The value of the diamond represents between 80 and 95% of the value of a typical diamond ring. Therefore, it is easy to understand why the accuracy of the diamond grading report is so vital.