The clarity of a diamond refers to the identifying characteristics of a stone that distinguish it from all other diamonds. These characteristics are known as inclusions and blemishes. Inclusions refer to the identifying characteristics in the interior of a diamond. Inclusions can vary from tiny pinpoints to large feathers and may even appear to be cracks in the diamond. Blemishes refer to the characteristics on the exterior of the diamond. Blemishes can vary from small nicks to large scratches, and there may also be extra facets and "naturals". Since no two diamonds have exactly the same identifying characteristics, you should become very familiar with the diamond you intend to buy. After color, clarity should be the second most important factor to consider when buying a diamond. The scale which determines the clarity of a diamond begins at internally flawless (IF) and proceeds through several grades of clarity depending on the size and number of inclusions present in a stone. The scale ends at imperfect. Diamonds that are imperfect in clarity have very obvious inclusions, which can be seen by the naked eye. Included Crystal Most common Often referred to as a "carbon spot", however, since diamonds are over 99% pure carbon, this term should not be used. The proper term is "dark included crystal." Usually consists of a black mineral called "magnetite" as well as other minerals such as garnet, peridot, and others. Pinpoints Tiny included crystals. Appear as tiny specks under magnification. Feathers Look like thin wispy bird feathers. Consist of two types of breaks: cleavages and fractures. Cleavages follow the crystal direction, much like following the grain on wood, and fractures do not. Both are cracks that can affect the durability of the stone, primarily in lower clarity grades. Can grow in size if it breaks the surface or is left long in ultrasonic cleaners. Cleavages are straight and fractures are jagged.