The 4Cs

The 4Cs are the shared vocabulary used by gemmological laboratories to describe a diamond. They are useful, but they are a description of a stone, not a ranking of beauty. Two diamonds with identical grades can look meaningfully different.

Carat

Carat is a unit of weight, not size. One carat equals 0.2 grams. Prices tend to step up at round milestones such as 1.00, 1.50, 2.00 and 3.00 carats, which is why a 1.90 carat stone can offer better value than a 2.01 carat stone of the same quality.

Colour

Colour is graded from D (colourless) through Z (light yellow or brown). In lab-grown diamonds the D to G range is widely available, so there is rarely a reason to compromise heavily on colour. Warmer grades can still look bright, particularly in yellow gold settings.

Clarity

Clarity records the inclusions and surface characteristics found under 10x magnification. VS1 and VS2 stones are typically eye-clean, meaning inclusions are not visible to the unaided eye at a normal viewing distance. Always review the plotted diagram on the report and the imagery rather than relying on the grade alone.

Cut

Cut is the only C determined entirely by human craft, and it has the largest influence on how a diamond performs. Cut grades are assigned to round brilliants; for fancy shapes, evaluate polish, symmetry, table and depth percentages together with the stone's imagery.