Andesite is a black to gray rock with between 53 and 63 weight percent silica (SiO2). Common minerals in andesite include plagioclase feldspar, pyroxene, and iron oxide. Andesites are very common on stratovolcanoes, where they form both thick lava flows and moderate-sized explosive eruptions of tephra. Andesites are erupted at temperatures between 900 and 1100 Centigrade.