» For the extinct cephalopod genus, see Andesites. Andesite 's an igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. The mineral assemblage's typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals. Alkali feldspar may be present in minor amounts. The quartz-feldspar abundances in andesite and other volcanic rocks are illustrated in QAPF diagrams. Relative… (More on Andesite)