Andesite is typically found in lava flows produced by stratovolcanoes above subduction zones. Because these lavas cooled rapidly at the surface, they are generally composed of small crystals. The mineral grains are usually so small that they cannot be seen clearly without the use of a hand lens or other magnifying device.

Some specimens that cooled rapidly contain a significant amount of glass, while others that formed from gas-charged lavas have a vesicular or amygdaloidal texture.