The size or weight, the shape, the colour and the clarity of each individual stone determine diamond pricing.
The size, which is determined by its weight in carats, determines part of the price of a diamond, and it goes up exponentially. A 0,10ct stone (a ten pointer) is not half the price of a 0,20ct stone (a twenty pointer). For example 0,01ct – 0,09ct stones are in one price bracket, then the price per carat jumps say from 0,10ct – 0,15ct and so on. If you find a 0,49ct ( which is very rare as they will try and cut it so that it hits 0, the price will be substantially lower than a 0,50ct, even though the diameter size might not seem that different to the average person’s eye.