Porphyritic Andesite

Type	Igneous Rock
Texture	Porphyritic
Origin	Extrusive/Volcanic
Chemical Composition	Intermediate
Color	Dark Green
Mineral Composition	Sodium – Calcium Plagioclase, Pyroxene, Hornblende
Miscellaneous	Hornblende Phenocrysts in an aphanitic (fine-grained) groundmass
Tectonic Environment	Convergent Boundary – both Island Arc-type and Andean-type subduction zones