Andesite is an intermediate extrusive rock characterized by dark grey, light purplish red or brown colours, a porphyritic structure, phenocrysts made of pyroxene, hornblende or biotite, intermediate plagioclase with a concentric structure, and a hyalopilitic or glassy texture. Andesite is widely distributed along the continental margin of the East Pacific Rim, which is also called the andesite line. Andesite is also widely distributed in eastern China.