It is a common misconception that the larger the diamond the better. A small colourless diamond of flawless clarity will be far more valuable than a larger stone with visible inclusions and a yellow hue.

Diamonds are graded from 'D' (without any colour) to 'Z' (tinted). Grade D diamonds are referred to as exceptional white, and this is accepted as the acme of purity in colour.

From the point of view of clarity, most stones, due to the way they are formed in nature, contain small inclusions of other minerals which can interfere with the way the gem refracts light. Rarely, perfectly clear flawless diamonds can be found, and these are most valuable. Inclusion grading is referred to in terms of SI (slight inclusion) VS (very slight) and VVS (very very slight). There are sub-gradings of 1 and 2 - thus a grading of VVS1 is better than a grading of VVS2.