Andesite



ExplanationAndesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. Basaltic andesite is a black volcanic rock containing about 55% silica. It is distinct from basalt and andesite in having a different percentage of silica content. Minerals in basaltic andesite include olivine, augite and plagioclase.
Sourcehttp://en.wikipedia.org/wiki/Basaltic_andesite, http://en.wikipedia.org/wiki/Andesite