Antofalla has erupted andesite and dacite, with dacite dominant and rhyolite a less common rock type; the entire spectrum from basaltic andesite to rhyolite has been found. Thin lava flows form most of the basalt-like rocks, which are subordinate at Antofalla. The rocks have a porphyric texture and contain phenocrysts including biotite, clinopyroxene, hornblende, ilmenite, magnetite, olivine, orthopyroxene, plagioclase, quartz and sanidine; not all of these occur in every rock.