An inaccurate and often misleading term, often used to imply that no internal flaws are visible to the unaided eye of a qualified diamond-clarity grader. Because it can be misrepresented by unscrupulous dealers, (even though it can also be used in helpful ways by honest jewelers) the term is not used by members of the American Gem Society for instance. It is also prohibited by the Federal Trade Commission, unless the stone meets the Commission’s definition of the term perfect.

Therefore, the best jewelers will only use this term if you need to use it, for common courtesy. It is better to stick with the proper technical Clarity Grades, to be sure everyone has the same understandings.

Usually, a grade of about SI-1 or higher on the clarity scale is flawless to the eye, but this varies by size, and type of inclusion, and by the lab doing the grading.

This is not the same as flawless or internally flawless, which are written as FL or IF, and are very very rare grades of clarity.

WP Glossary Term Usage