Among the four "Cs" of diamond value, "clarity" embraces the inner appearance of diamonds. In keeping with the precise nature of determining diamond value, clarity has its own scale of measurement.

Nearly all diamonds have inclusions. Bubbles, specks and lines are inclusions that give each diamond its own inner signature. The clarity scale accounts for these microscopic imperfections. Gems with the fewest inclusions are the rarest and costliest. So minute are many inclusions that they can be seen only under 10-power magnification.