Inclusions are minerals or fractures that can appear as tiny crystals and can look like clouds or feathers. Some are caused by the conditions present when the diamond was formed, some by the cutting process or after the diamond was cut.

Jewellers use a magnifying loupe or binocular microscope to view inclusions. These instruments allow them to view a diamond at 10x its actual size so that any inclusions are easier to see. The value of a diamond can be affected by the size, number and position of inclusions. Since there are very few flawless diamonds found in nature, these diamonds are therefore much more valuable.

The Gemological Institute of America has established a standard scale for clarity, ranging from F (flawless) to I (included). The scale is based on the visibility of inclusions at a magnification of 10x. This magnification is the accepted standard used in North America and most other countries.