A crystalline igneous rock that consists largely of alkali feldspar (typically perthitic microcline or orthoclase), quartz, and plagioclase (commonly calcic albite or oligoclase). Its average grain size is 0.04–1.0 in. (1–25 mm); finer-grained rocks of this composition include rhyolite and aplite, and coarser-grained ones are granite pegmatite.