What does "cloud" refer to in gem evaluation?

In gem evaluation, the term "cloud" specifically refers to any hazy or milky area within a gemstone that does not fit the definitions of a feather or inclusion. These cloud-like formations can affect the clarity of a gem, which is one of the crucial aspects considered in grading gemstones. Clouds can come in varying degrees, and while they can slightly reduce a gemstone's brilliance or transparency, they are typically evaluated in conjunction with other clarity characteristics to determine the overall quality of the stone.

The term is distinct from other types of inclusions, such as feathers, which refer to specific types of internal breaks or fractures, and fingerprint inclusions, which are unique patterns that resemble a fingerprint. In contrast, the definition of cloud is broader and encompasses various haziness that isn't specifically classified as a feather or an inclusion, marking it as an important concept in the field of colored stone evaluation.