Petrographically, the composition of the cluster ranges from andesite to dacite with SiO2 ranging from 62.8% to 65.7%. Andesites appear as lava flows while dacites form lava domes and dome complexes. The rocks from the main Aucanquilcha volcano are uniformly dacitic and show little evidence of temporal variation in their composition. Potassium content ranges from 1.5 to 4%. Plagioclase is the dominant component of the magma. Clinopyroxene+orthopyroxene+amphibole (hornblende and pargasite) or amphibole+biotite+minor amounts of pyroxene are subordinate components. Apatite, ilmenite, magnetite and zircon can also be found. There is evidence of magma mixing and mingling.