The clarity or purity of a diamond is determined by the number, size, brightness and location of the internal and external characteristics, important structural phenomena and transpency.

The impurities inside the stone are inportant for the clarity grade. External characteristics on the surface of the stone only have an influence on theclarity grade if they are sufficiently noticeable and if the stone is not internally flawed. the stone is examined with a loupe and a microscope, during which all characteristics having a bearing on the clarity are noted down.