The Diamond 4Cs: Cut, Colour, Clarity and Carat

For round brilliants, cut usually has the greatest effect on how bright and lively a diamond looks. A well-cut stone can make slightly lower colour or clarity grades far less noticeable.

An eye-clean diamond has no inclusions visible to the unaided eye at a normal viewing distance. Many VS2 and some SI1 diamonds are eye clean, though it depends on the type and position of each inclusion.

For most people, yes. G and H sit in the near-colourless range and generally look white face-up, especially in white gold or platinum settings.

Not necessarily. Most fluorescence has no visible effect, and faint to medium blue can even make lower-colour stones look whiter; only occasionally does very strong fluorescence cause a hazy appearance.

Carat measures weight, not dimensions. Two diamonds of the same carat weight can look different in size depending on shape and how deeply they are cut, which is why millimetre measurements are worth checking.

Ct refers to the weight of a single diamond, while ctw (or tcw) is the combined weight of all diamonds in a piece. A 1 ctw ring with several stones will look quite different from a single 1 ct diamond.