Plagioclase feldspar is the most common phenocryst, but pyroxene, amphibole, or biotite may appear. The feldspars frequently occur as strongly zoned phenocrysts. Most andesites are flow banded, though not so conspicuously as rhyolites.
Andesites range from white to black, but most are dark gray or greenish gray.
Andesite is abundant as lava flows and as fragments in volcanic breccias, tuffs, and mudflows. Andesite also forms small intrusive masses. An increase in the quartz percentage marks the gradation of andesites into dacites.