A shared language for diamonds
The 4Cs give buyers, sellers and laboratories a common way to describe a diamond's quality. A WGI Diamond Grading Report records each of them, together with shape, measurements, polish and symmetry.
Cut
Cut describes how well a diamond's facets interact with light. Proportions, symmetry and polish determine how much brightness, fire and scintillation the diamond shows. Cut is the one C shaped entirely by human craftsmanship.
Colour
Most white diamonds are graded on a scale from D (colourless) to Z (light yellow or brown). Differences between neighbouring grades are subtle and are judged by comparison under controlled lighting.
Clarity
Clarity describes internal features (inclusions) and surface features (blemishes). Grades run from Flawless through VVS, VS and SI to Included, based on what is visible under 10× magnification.
Carat weight
Carat is a unit of weight: one carat equals 0.2 grams. Two diamonds of the same weight can look different in size depending on their cut and proportions.