A large majority of the iron castings produced are of gray iron. The generic term "cast iron" is often used to refer to gray iron. The name comes from the characteristic gray color on the metal on a fractured surface. This is caused by the presence of fine graphite flakes in the iron.
The flake graphite in the gray iron provides it with excellent machinablility at hardness levels that provide superior wear characteristics, the ability to resist galling under borderline lubrication, and unusual elastic properties that provide excellent vibration damping.