Most diamonds contain a few minor flaws or “inclusions” that effect their clarity.
An inclusion is any spot, scratch, bubble or line that occurred when the diamond was being formed deep in the earth.
Most inclusions are not visible to the naked eye, so gem laboratories use a magnifying glass (at 10x magnification) to determine the amount, size, position, nature, and color of the inclusions.
The clarity of diamonds range from “flawless” to “included”.