ANDESITE

Andesite is an extrusive igneous rock consisting primarily of plagioclase plus pyroxene and/or hornblende. Biotite, magnetite, quartz and sphene are common constituents. 

Andesite has the equivalent composition to the plutonic igneous rock, diorite.

Andesite is named after the Andes mountain range. These rocks are found near the subduction zones of ocean tectonic plates, along continental margins.