Diopside, the characteristic component of diopside gneiss, is an important rock-forming silicate mineral found in many metamorphic and igneous rocks, as well as meteorites. A member of the pyroxene family, diopside is part of a chemical replacement series that also includes hedenbergite and augite. Iron and magnesium ions can be freely substituted between these three minerals. Although it is frequently a lustrous white or green in color, diopside may exhibit a variety of hues and patterns. A blue form, for instance, is found occasionally in Italy and is called violan, while a dark type of diopside with rutile needles aligned in a stellar-like formation is commonly known as star diopside.