Microcline (KAlSi3O8) is an important igneous rock -forming tectosilicate. It is a potassium. Microcline typically contains minor amounts of sodium and pegmatites. Microcline forms during slow cooling of orthoclase ; it is more stable at lower temperatures than orthoclase. Sanidine of alkali feldspar stable at yet higher temperature. Microcline may be clear, white, pale-yellow, brick-red, or green; it is generally characterized by cross-hatch twinning that forms as a result of the transformation of monoclinic microcline.
The chemical compound name is potassium aluminium silicate, and it is known as E number reference E555.