Carat, colour, clarity and cut describe a diamond’s weight, colour, clarity and cutting quality. Consider them together when comparing stones.
Cut
The cut determines how a diamond reflects light, its sparkle and fire. It's the only one of the four criteria shaped by human hands, and many regard it as the most important.
Color
Colour is graded on a scale from D (completely colourless) to Z (clearly tinted). The more colourless a white diamond, the rarer and usually the more valuable it is.
Clarity
Clarity describes how free the stone is of tiny inclusions, assessed under tenfold magnification with a loupe. Fewer and smaller inclusions usually mean more brilliance.
Carat
Weight is given in carats (1 carat = 0.2 grams, divided into 100 points). Larger diamonds are rarer, so the price rises disproportionately with weight. Only the interplay of all four Cs produces the value.