4 Cs

Colour, Carat, Clarity and Cut... these are the four important characteristics by which gemstones (especially diamonds) are judged. Of the four, cut is the most important one, the one that brings the other three qualities together. Sacrifice cut for carat weight and you have a stone with poor colour diffusion and bad light reflecting properties. If the stone is not studied properly and the inclusions are not well disguised within a stone, the value plummets.