A white, gray, brick-red or green mineral of the alkali feldspar group: (KAlSi₃O₈). It is the fully ordered, triclinic modification of potassium feldspar and is dimorphous with orthoclase, being stable at lower temperatures, it usually contains sodium in minor amounts. Microcline is a common rock forming mineral of granitic rocks and pegmatites, and is often secondary in orthoclase.