Orthoclase is a common alkali (or potassium) feldspar mineral that can be pink or white in colour.

Orthoclase is a typical feldspar that is the dominant mineral in coarse-grained silica-rich igneous rocks like granite and syenite. It can also form particularly large crystals in pegmatites.  Common in many metamorphic rocks, it also occurs to a lesser extent in sedimentary rocks.

In igneous rocks orthoclase is common and may sometimes, when white, be confused with Na-plagioclase.