Sample F20: Hornblende Andesite



Amphibole (hornblende) and plagioclase phenocrysts set in a sub-trachytic groundmass (note how the plagioclase laths in the groundmass appear to "flow" around the phenocrysts).  The basal sections of the hornblende phenocrysts show the characteristic 120˚/60˚ cleavage angles characteristic of amphibole.