Perfectly clear diamonds are extremely rare. Most often, small foreign crystals or microcracks can be found in their structure. To see them, use multiple magnifications.
Subtle inclusions can serve as a "fingerprint" for the stone, confirming its natural origin. On the other hand, large blackouts reduce the brilliance of a diamond, while large cracks can lead to splitting.
The fewer such defects in a stone, the higher it is valued. According to the degree of purity, diamonds are divided into groups. As with color, different countries use different designations for stone clarity.